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FAQs About Water Changes for Marine Systems: Automation

Related Articles: Marine Water Change, The 'Perfect' Water Change Regimen? by Scott Fellman, Water Changes, Exchanges by Anthony Calfo, Captive Seawater Quality, General Marine Maintenance,

Automatic (and easy) Water changes 8/23/11
Hi Gang,
<Hiya - Darrel here>
I'm ready to order my tank and sump and just want to run my 'automatic' water change idea/design past the experts.
<Well ya got ME instead! LOL>
The display tank overflows into the sump and is then pumped back to the display.
<That's a good start, Rick. In our first version, the display tank overflowed to the living room floor. The wife was upset and the fish were none too pleased, either>
As per the Calfo design, the sump has an overflow drain-hole drilled at essentially the same height as the water height within the return pump chamber
<So if more water drains from the tank than the sump can handle, it drains via this hole rather than over the top and onto the floor>
I've read numerous designs utilizing solenoids, valves, and the such for water changes, but what is wrong with simply having an open drain from the sump at this operating height. Once a day, salt water is pumped into the display (via timer and known corresponding volume), and obviously the same volume exits the overflow hole -- water change is done (and many researchers seems to favor the smaller frequent water changes as well).
<Yes. The 10% per week guideline has generally been the balance between marine life needs and hassle-factor. The fish themselves would be happy with smaller, more frequent changes>
Salt water supply can be made up weekly or bi-weekly as per required to have enough for the small daily changes.
<The only thing SO FAR is that you have a single stage system -- that is to say that as you are adding new water to the system, some of that new water is also draining out your sump hole.>
<Hmmm - sump hole? Is that something that sounds dirty but isn't? But, I digress>
<Let's talk a walk for a minute. Let's take a 10 gallon tank and 10% weekly water changes. At the end of the first week, you have 10 gallons of water that is a week old. After you drain 1 gallon and refill with new water, you have 9 gallons that is a week old and 1 gallon that is new. At the end of week 2 you drain another gallon of which 9/10 is two weeks old and 1/10 is one week old. Next week you drain 8/10 of a gallon of 3 week old water, 1/10 of a gallon that is two weeks old and 1/10 of a gallon that is one week old. The point being that even with regular water changes, the closed system inexorably degrades and becomes '¦ um ... something unbecoming. Despite all our efforts in the art & the science of fish keeping, the main thing that keeps our creatures alive is their ability to adapt to this slowly decaying environment and our inability to compensate. Anyway, in your system you add a very slight additional problem in that your incoming new water is mixing with the very water being pumped out. -- That Said -- I wouldn't lose sleep over it>
OK, what can go wrong ...
<Always my favorite challenge>
If the power goes off, water in the sump raises up and drains out the overflow hole (I've ensured the sump can handle the initial Water-In-Transit surge). When the power comes back on (and regardless of how many times it goes on and off during that day), the tank will continue to operate (with a reduced volume), until the next water change which as mentioned will be done on a simple timer system within a day.
<Right - the Display tank drains until the water reaches the level of the drain and the sump takes up some of that water - until it hits your sump drain hole. As long as the return pump is low enough to pump the initial gallon (or whatever) back into the display tank without running dry, then you're covered here>
The top-up system will operate on a 2-float set-up, with the shut-off float slightly lower than the evaporation top-up float ... this ensures that a large amount of fresh water is not pumped into the system to replace the Water-In-Transit once the power comes back on. Bottom line, whenever there is a power outage, the system will drain water and then operate at a reduced volume until the next daily water change. The amount of water lost to evaporation before the next daily water change will be insignificant. Allowance has been made to ensure the system still has 'enough' water to operate after losing the 'Water-In-Transit' amount.
<OK>
If the saltwater supply pump 'sticks' ON, (pump will only operate for 5 minutes max) and essentially this error results in a water change.
<Until it runs out of supply water, but yes>
If the freshwater top-up pump 'sticks' ON, (again the pump will only operate for 5 minutes max. with small RO tubing) and this water enters the system adjacent to the overflow hole in which a portion would exit the overflow drain having a minor affect on the system.
<Minor effect being defined as to how long it stuck on '¦ because every second past actual evaporation is diluting your marine mix>
Naturally, there would be manual-override to perform a larger water change if desired/required.
<Naturally>
As always, appreciated your feedback.
Rick Campbell
<From a purely engineering standpoint, you have all the bases covered. Please be mindful of the old adage that says "The more complicated the plumbing, the easier it is to stop up the pipes">
<I think you have a system in place '¦ and we'd like to have a series of pictures as you fabricate, assemble and implement your project, Rick>
<In my automated systems, I use sprinkler timers, valves and pump relays. I drain water by turning on a pump connected to Station 1 for x minutes and then I refill by turning on a pump connected to Station 2 that is wired through a float valve switch. This way I conduct the drain to a specific point, finish that and then begin the fill cycle -- all of which is essentially the same idea you have>
<Send us pictures and a write up on how it goes!>
Re: Automatic (and easy) Water changes 8/23/11
Darrel,
<Hiya>
I was just thinking (believe it or not) ... for your auto water change, doesn't your freshwater Top-up "kick-in" as soon as you start draining Station #1 ... diluting the system?
Rick
<NO - because the fill is tubing wired to Station #2>
<So what happens is: Station #1 cycles for 2 minutes which turns on pump #1which drains. Then, when station #1 cycles off, Station 2 cycles ON for 5 minutes. THAT turns on a sprinkler valve which passes the fill water on. Station #2 is wired in series with an electric float switch ... so the level must be down AND Station #2 must be on in order to fill>

Make up water for my aquarium
Automated Water Changes 6/30/09
I have a 300gal tank and a 75gal wet dry I want to have a auto make up water for my system could you tell me how.
<This can be done, but is a fairly complex DIY project to make safe and reliable. You first of course will need a tank or vessel to hold the makeup water. Then you will need a couple of pumps, plumbing between the tank and this holding tank, plumbing coming out of the tank to wherever you want your wastewater to go, and a few timers. The first timer will need to shut off your sump return pump. The second will start up at this time and pump the water out of the sump. How much water should be determined by where the pump inlet is at, not how long the timer runs the pump for. Now the timer running the pump in your holding tank can come on to start pumping in the new water. Ideally this amount of water too should be regulated by the pump inlet in relation to the amount of water in the tank.
Another route or failsafe that you can add in here are electronic float valves to shut these pumps off at the appropriate levels. Now, between the two tanks you will need a siphon break so one tank does not siphon back into the other at some point. As for automating mixing the salt, I just wouldn't. The easiest is to get a salinity meter and just add a little salt at a time with a powerhead circulating the holding tank. I believe in
and use a refractometer myself. It is a bit more work, but I do feel it is much more reliably accurate. With all of this being said, I have had such systems on my tanks in the past. Now I just opt for all of the above
manually run with ball valves by me, there is still no hauling water. I just don't trust timers and float switches to never fail! Scott V.>
Oh, one more thing to add. If you have an ATO system it will of course need to be shut off during the whole process. Scott V.

Automated water changes for mini-reef Hello, and thanks for the great website and instructive information. <thanks kindly... please keep reading, learning and sharing> I'm interested in attempting the following experiment: to maintain a 180 gal. community mini-reef system with automated water changes from the regeneration (the rinse water that cleanses the ion-exchange resin bed) from my household water softener. <I see some likely problems already if your household softener uses potassium or sodium chloride to recharge: imparting chlorides which skew alkalinity in the aquarium for post treated water... OR...(your case) the impart of hardened "purged water" which has mostly useful hard water elements (exchanged for chloride by the softener) BUT(!) also has un-exchanged sodium chloride. This unregulated NaCl allowed into your aquarium without the other balanced minerals and trace elements of seawater will naturally effect your SG but without the other necessary elements. In simpler terms... you can add enough NaCl table salt to a glass of water that gives you a desired reading for marine life, but without the trace elements... marine life will die in this salted water even though the hydrometer says differently> We use a 38,000 grain "on demand" water softener (using sodium chloride) <Houston we have a problem...> and a RO system. (THE RO brine is used for another application -- a humidifying water fountain). The hardness of our municipal tap water is approx. 16 grains. It is chlorinated, but has low (undetectable) total dissolved solid, phosphate, copper and iron content. Each regeneration uses approx 35 gallons, and regenerates approx. every 5 days. Approximately 3lbs of salt is used for each regeneration: <Ughh> The water chemistry of this "brine" consists mostly of sodium chloride, calcium and magnesium. <Oh, ya!> I have 2 pH readings, 8.1 and 8.2 I'd like to have this water run through some activated carbon and a specified amount of additional synthetic sea salt -- before it hits the sump. <sorry... how do you reckon the incidental plain salt carried in? Even if you could easily measure it, do you really want to get into making your own synthetic trace element slurry to dose and temper the stray plain NaCl?> The tank would be appropriately fitted for overflow drainage. <way too complicated here, bud. Your best bet would be to get a separate (small is OK) 2-column de-ionizer and completely demineralize this water if your goal is saving water. The high pH of this effluent that will be lost through the DI is a small loss and easily/cheaply recovered post treatment> The issues, as I see it are as follows: 1: Maintaining the specific gravity of the tank by fine-tuning the requisite additional salt; (including fiddling with the evaporation rate, by changing the amt. of uncovered surface area.) <a complete nightmare... complicated and recommended only if you enjoy the challenge and are a chemist> 2: Accounting for an accelerated removal of trace elements (strontium, etc.). <accelerated? They were never there in the first place. Not sure we are on the same page here. I am talking about you reckoning the sodium chloride that you are bringing in with this rinse water but without the slurry of balanced trace elements to make SW> Before I reinvent the wheel, do you have any information about other attempts in this area? <no one bothers when time and expense are issues. This would have to be a personal challenge for you, because there is no practical reason otherwise for doing it. The irony is that your tap water through carbon is probably the best water could you have in the house for a marine tank. Reconstituting pure DI water is probably second.> Are there any flies in the ointment I'm missing? <a whole swamp full of flies, brother!> Other considerations? <this really all boils down to not bringing plain salt into the make up water or being a brilliant chemist with a lab to check the daily/weekly variances and compensate for them with your own home-made synthetic sea salt mix> -- e.g. are there some reef species that would be more tolerant to this? <cruel and unnatural to do so... doesn't happen in the wild> Species to avoid? <Ha!... All<G>> Are there other automations to help minimize other tank maintenance, <I can forward you a chapter from my book about setting up automatic water changes with solenoids> such as substrate maintenance? <thin substrate, strong water movement and active sand sifting animals> What other issues should I consider? <hmmm... I'd suggest that you try treating this more like a hobby instead of a science, my friend :) ... unless you truly enjoy the science more than the organic living components (our fishes and corals!)> Thanks!-Frank Pagoda BTW: I plan to keep a journal on this project & publish my results to help others who may be curious about this operation. <indeed, that would be excellent at any rate. Kind regards, Anthony>

Automated water changes for mini-reef Whew! I haven't been sobered up that aggressively since college mid-terms! <Ha! With a college flashback like that, did you also suddenly get the munchies too? And for lack of a beer at hand, chug your scalding hot coffee chanting "Go. go...go...go...GOOOOOO!" in your head? Just checking?> Your sense of humor and gracious style, Anthony, is why when you ring in folks like me (and you sure did) we laugh along....good job! And thanks for the good feedback. <Wow... thanks kindly :) But I was really just taking the long way around the barn for calling you a sadist with mad scientist tendencies. I'll take the credit just the same <G>. Heehee...> Your reasonable protestations aside, let's assume I (pigheadedly!) go through with this experiment. <OK> Should I seek out a SW product that is markedly higher in balanced trace elements than others? <that depends on how involved you want to get here. If the science of it isn't appeal in the purist form... and you just simply want to make it work: my advice would be to simply purchase the semi-solid synthetic sea salt concentrates they make for the big commercial operations (actually quite economical... but you must mix every time EXTREMELY well or make whole batches (400gall) at a time). These SW slurries have everything in it you need except plain salt. Then... you will only have to calculate the influx of sodium chloride with the source water and supplement proportionately> Is there a trace element compound available without sodium chloride? <yep... most of the big manufacturers make it. Best to seek an aquaculture supply house for this. Fritz used to make such a product for public aquariums and shrimp/food fish farmers.. perhaps still do?> Maybe the trace element/SW slurry (including the correct amount of salt to balance the brine) could be set below the activated charcoal/carbon, ready to be washed into the tank with the regenerated water. What other suggestions do you have to make this work? <Jack Daniels... by the gallon> I know using that automating a system with inferior water is complicated, ultimately may not work, and is repugnant to many. But the allure of utilizing water that is so close to ideal, and is generated a mere 5 feet away from the tank, and can lop off a HUGE chunk of time, and is an intriguing alternative to the conventional way -- is all too enticing for me. <some merit to it, some extra complications too. The high pH and high mineral content are easily provided/supplemented and cheaply too otherwise. You may find that using this water is not time saving at all, and simply resort to carbon filtered tap water> BTW, I will NOT jeopardize any marine wildlife with this Dr. Demento contraption. <understood my friend> Live rock will be added only when I can easily maintain the correct SW chemistry. Finally, I agree with your suggestion that I treat this more as a hobby than as a science. That's what I'm doing! Rather than anally adhering to scientific rules set in stone, I'm trying a different path to the same destination. <you're a heroin addict, aren't you? Ahem,... I mean... "Why yes, I concur wholeheartedly with your reason and rationale for embracing the science of aquariology without becoming enslaved to it." Errrh... or something like that <G>> From where I sit, my friend, that's the approach that makes mini-reefkeeping a hobby. Thanks again, and do let me know your additional input to this unconventional approach to make and maintain safe sea water. With great appreciation, Frank <best regards in this endeavor... we'll watch for you on the news. :) Anthony>

Plumbing for water changes I am plumbing a new tank with a sump. I was wondering what would be the easiest way to set it up to do water changes. Can I add a T with a ball valve off the return line so I can just open the ball valve and let water go into a bucket and shut it off when finished? <Turn the pump off and get the water from the back siphon> Then I would just add water back into the sump. I should be able to do this without turning off any power and not effect anything (I think). <Maybe...> I will be changing about 2gal a week. <Great sketch! Let me state that I personally don't use a water change device of this nature. However, I did research this type of idea when I set up my tank. I assume that you are planning on using flexible PVC for your lines. It would certainly be the easiest material to manipulate. My concern for your proposal is the pressure that the water will be under as it is leaving the return line and entering the bucket. You will be drawing water very close from the return pump and this water may splash around and spray a lot more than you want. Since I don't know how large your return pump is it's hard to make an accurate estimate of the pressure involved. If the pump only moves a couple of hundred gallons or so, you may be fine. If the pump is large say over 300 or 400GPH the pressure may be strong. I don't know for sure the repercussions but the above statements are my initial assessment. Consider this: I assume your return line is releasing water in the main tank under the tank water level. As an option you could plumb the tank exactly the way that you have planned...If the pressure is too great, you can always shut off your return pump and let the back siphon water flow through your "T" and into the bucket! From your drawing it looks like this "T" is also a shutoff valve which is exactly what you will need. If your pump is submersible realize it may heat up your water. Be sure to plumb shutoff valves after your pump so that it may be removed entirely from the system if the need arises. If your pump is external you need shutoffs before and after the pump. Lastly, Prizm skimmers have a poor reputation among hobbyists. Complaints include too much noise and inefficiency. David Dowless> Shaun Nelson

Plumbing for water changes Thanks for the info. Yes I am using flexible pvc from the pump to the T. I will be using a MAG 7 for the return. I thought with a ball valve I would be able to regulate the water going into the bucket? <That is plausible. Should work okay> Anyway I will do like you said and try it with the pump on and off. And yes the Prizm Sucks, I already bought it. <Sell it on EBay! David Dowless>

Can you make a recommendation on the automatic top off? Right now my R/O unit goes to a 80 gallon reservoir which I will use for my premix. I was thinking of teeing off the existing supply to the 80-gallon reservoir to the sump and controlling the flow with a Kent marine float valve. In other words, the R/O unit would feed both the 80-gallon reservoir and another line directly to the sump. Kent marine, however, does not recommend having a float valve in the sump connected directly to the R/O unit. for some reason this is bad for the solenoid, since the constant evaporation from the sump will keep the R/O unit working constantly or at least turning the solenoid on and off constantly. The recommendation was to get yet another reservoir to which I would periodically pump water from the existing 80-gallon reservoir. This second reservoir would be solely for fresh water and would gravity feed the sump and be controlled by a float valve. This second reservoir would have to be refilled every week or so, so the automatic top-off would not be fully automatic, just automated during the week. Any thoughts on this would be appreciated. <There are two ways to do this depending on your system. The above system allows you to buffer your top-off water as needed, but is less automated. The opposite idea works as well, automated with dosing pumps, calcium reactors, etc. You need two containers as above. The main reservoir is fed by the RO unit controlled by the Kent float. The pre-mix container should be the container that is periodically filled when needed, not the top-off. The top-off system can then be run with a small pump in the main reservoir, controlled by a solenoid in the sump (either DIY or one of the commercially available units) which refills the sump automatically. Check out marine set-ups at WetWebMedia.com Craig>

Re: automatic top-off Two perceived advantages of not using the main reservoir as the automatic top off: (1) The R/O unit isn't running all the time from the constant dribble replacing evaporation from the sump; <This is a non-issue, RO's that feed drinking water tanks have the same intervals/use. It will run as long as required to fill the reservoir, regardless.> (2) in the event of malfunction, only a limited amount of fresh water gets dumped in the tank. <This is a good reason to go with the gravity fed top-off of limited volume, only so much water can be accidentally added to the system.> What the perceived advantages of what you propose? Solely automation? The task of refilling the automatic top off seems hardly burdensome. It's a flip of the switch. <I got the feeling you were concerned with automation, if not, I would go with what works best, is safest for you and your inhabitants. Enjoy! Craig>

Cleaning The Substrate Hello <Hi there- Scott F. with you today!> I have dug around in your FAQ's for a while now and haven't found exactly what I'm looking for so sorry to bother you. My situation is this I have a new FOWLR w/4" SB and am thinking ahead in my setup in order to try and make my monthly water changes go a little smoother. I am planning of setting up a "permanent" section of tubing that will run from the bottom, left, rear corner of my tank to underneath my tank. I then plan on putting a valve or even better yet one of the valves from a 350 magnum on there to shut on and off the water flow so my water changes will take minutes! <Innovative...an interesting idea...certainly can work... Now I plan to have a goby or other sand dweller in there as well as numerous Turbo Grazers. Now for the question: Is it absolutely necessary and vital to vacuum the upper 1/2" of my substrate during my monthly water changes? <Really a subjective thing...I do not consider it mandatory...> Thanx again. Kevin Conner <And thank you, Kevin- for stopping by. Good luck! Regards, Scott F>

Cleaning The Substrate (Pt.2) "Innovative...an interesting idea...certainly can work..." wait till you see what I plan to do with this Prizm protein skimmers collection cup ;) <Now, if you can just figure out away to keep mustard squeeze bottles from clogging, you may be up for a Nobel prize! Regards, Scott F>

- Water Changes - <Greetings, JasonC here...> I came up with what seems to be a great idea for water changes although I'm sure you will tell me that someone else has already thought of it. <Maybe so, maybe not...> Please let me know if you can see any potential problems with this idea. This is my first reef aquarium. The tank is 165 gallons and I've got a total sump capacity of 50 gallons. There is a small space behind the tank (4'X4'X4') and I thought I would stack two 25 gallon tanks there. The bottom tank would be for drain water (I have no way to plumb to a drain directly) and the top tank would hold fresh saltwater. I've figured my maximum water level in the sump to be 9" in order to accommodate the extra 15 gallons from the tank that I calculated would get there in the event of a power failure. <The word 'calculate' makes me very nervous here... I would do a wet run with freshwater as part of the leak-check process and make sure these 'calculations' bear out.> I was then going to install a small bulkhead in the sump at 9" and plumb it to the drainage tank. The top tank would gravity fresh saltwater back to the sump. <I'm guessing here that you will have valves between the two auxiliary tanks and the sump so that you will determine when it's time to start the drain process and refill...> I figure as long as the bottom tank is empty when the top tank is full and if the top tank never holds more than what the bottom tank will hold at the 9" level, I am not really asking the sump to hold any additional volume. The only weakness I see is if the drain line gets plugged, but I suppose I could size it to minimize that potential and add a float switch to stop the fresh saltwater flow if the sump level is too high. My goal would be to balance the flow of fresh saltwater to the point where I would need a refill once a week, about a 20 gallon water change. <Well.. I'm not sure 9" of water in a 25 gallon tank is going to net you a 20 gallon change - probably more like 10 gallons - you should measure this to be certain. Likewise, with the fitting at 9" between the sump and drain tank, you will not get more water than this [9"]into the drain tank without a pump. Also... if I read this correctly, you want to continually drain some amount of water into the drain tank and replace the water from the sump [at a constant rate] from the fill tank? Is that right? This makes me nervous for a couple of reasons, but mostly because it's very hard to match flow rates - very easy to over-fill or under-fill the sump and perhaps have a pump run dry. Also... if my reading of your description is correct, wouldn't you also stand to have some of the fresh mix-water going into the drain tank? I'd think you'd want to avoid that.> At that time, I would suck out the bottom tank and refill the top. Is the above method really any better than just doing a 20 gallon change all at once every week? <Well... I can see why you would want to lessen the labor, but I think you may have to end up hauling buckets.> Is there a reliable type of metering valve to control such a small flow? <I don't know of any that would hold up to use in saltwater - best to use ball valves although they don't meter as well as others.> How would you maintain SG? Mix the fresh saltwater at a slighter lower SG to balance evaporation or just test and add fresh RO water as needed? <No, typically top off water should be water without salts - the salt in your tank doesn't evaporate so that any addition of water with salt in it will increase your salinity.> Assuming 85*F as a maximum ambient temperature during the summer, what does a typical reef aquarium this size with metal halides lose to evaporation in a week? Gallons? Tens of gallons? <In a week? My guess is tens of gallons - I used to put about two gallons of freshwater in my 180 a day.> Thanks, George Nikolich <Cheers, J -- >

Auto top-off RO water in reef tank If you use raw RO water for auto top off what should be added. I do not used Kalk. -RGibson <Well, Kalkwasser would be nice. Other than that, the water should be aerated and buffered. -Steven Pro>

The Automatic Aquarium Water Changer Hi there, I am emailing from the UK. I have seen The Automatic Aquarium Water Changer in several books, and also on the internet. I have asked about this equipment in pet stores, but not been able to find it. Do you know if there as a seller of this in the UK? <You might try the folks at TMC: http://www.tmc-ltd.co.uk/ If anyone knows where/if this product can be procured there they will. Bob Fenner> Regards Keith Charlton

Automated Water Replacement System Hi Robert! How are you? <Fine> I was wondering if I could get your expert opinion on this setup. I implemented an automatic drip system for my 72 gallon reef tank. I was hoping through the constant water exchange that I could maintain pure high level quality water in this environment. <A good approach> My system is basically set up like this... I have a 20 gallon tall hex mixing tank under my 75 gallon reef tank that fills up very slowly (with 1/4" tubing from my RO unit located in the kitchen). The water fills up to the 10 gallon mark set by a large toilet like float switch, (Home depot). The large float switch is enclosed in a plastic tube & clamped to the side of the tank . This tube prevents water from getting inside the switch and keeps the float mechanism basically pretty clean of salt free. <Okay> I have a small pump that is mounted 3 inches down from the high water mark in this mixing tank. The pump is always on & constantly pushing water pressure through 1/4" inch tubing over to my Wet Dry sump which has a very small float switch (Polypropylene Valve Body Polypropylene Float - http://www.mcmaster.com) that is mounted about 1/2 foot down from the top of the sump. <With you so far> I also have a small powerhead in the 20 hex that is constantly on and circulating the water all week long. I try to keep the SG and temperature at the same level with what is in the tank. Saltwater drips out of the main tank very slowly into a bucket and new RO saltwater drips in to the sump very slowly (drips in at approx. 2 gallons per day). I also add one cup of RO water without salt for evaporation each day. I am hoping that I am getting a true balance here. <Me too> My question is... Is it ok to utilize a slow water replacement system like this and how beneficial are it's affects in overall water quality? Am I disrupting the balance or chemistry of the water or am I improving the overall balance... removing nitrates, keeping PH level high? <Very beneficial> Do you know of anyone who does this? <Most public aquariums, many breeding facilities> Is it ok for me to do a 5-10% water change each Friday in additional to the slow water replacement? Really appreciate your comments. <Sure, but likely unnecessary. BTW, so I can sleep tonight... have you tried shutting off power to one, all pumps to "see what happens"? Any overflow fail-safe mechanisms in place? Be chatting. Bob Fenner>

Re: Automated Water Replacement System Yes, Actually, as long as the float mechanisms in the mixing tank and sump do not get clogged (left in open position) I am ok. If the power goes off only a few gallons of water from the main tank will come down into the sump. Water does not go back into the mixing tank from the sump. <Mmm, I would still have... an overflow box... curtain of sorts around the edge... excuses/explanations aplenty on hand...> The RO water comes in very slowly to the mixing tank and I usually close the valves once I have the 10 gallons needed for daily water exchange. I then open the valves once again at the end of the week to fill the mixing tank once again for weekly water change. <What if you forget?> I would not leave this operation running for a few days unattended.... <How about a timer with solenoids then?> actually I have lost a few nights sleep worrying about it but when I turned off the power I felt a little better! I should probably check the valves every so often. <Sorry to be such a "worry wart"... just have had an amazing number of spilled water mishaps/accidents over the years. Bob Fenner>

Re: Automated Water Replacement System If I do build some kind of redundancy into this setup and it is fail proof do you know if there is any kind of market out there for my system? Would you know of people who would care to set something up like this? It was not that expensive... just the RO unit. <I do think there is some "build-able" market for this arrangement... Many water treatment tools in place now... and many more to come on-line in coming years... Worth investigating, test-marketing. Bob Fenner>

Topping off Hi Bob, When you top off a tank to replace evaporated water, should you use seawater with a lower salt concentration? <No... unless you're trying to raise the spg... just freshwater. Bob Fenner> Tony

Re: topping off That is what I thought but I wanted to be sure. Thank you for the quick response. <You're welcome my friend. Be chatting. Bob Fenner> Tony

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