Neptune Aquatics

Looking for help in building water change Station

1) Well from what I gather "tee on output of freshwater" you essentially fill up both containers at the same time, or at the very least one full container of RO water, then turn the valve which will drain half of the water into the SW container as the levels equalize, then you fill up with RO water so both are completely full, then turn the valve to isolate the RO container, throw in salt in the SW container, mix and have a container of SW and one of FW. Now as you use the SW container you get to a point of wanting to make new stuff, so you do the same trick of opening the valve on the RO container which goes into the SW container, however any residual amount of SW will mix with the RO water, including what is in the RO container, now it may not be a perfect mix but you'll have some, how much depends upon drift velocity of ions in water or some crap like that, and also depends on how much SW was left in the container. To see a "worst case" what if you opened the valve when the SW was completely full, the SW is not going to magically stay isolate to the SW container side even though both water levels are at the same height, now extrapolate to smaller and smaller amounts of SW in the container and it's not too hard to see that there will be some cross contamination. Now that may be ok for you, but as someone who doesn't use ALL the SW when it's time to mix up a new batch (just in case of emergencies, I like to have a full or nearly full container on hand if possible always) this would be problematic for me, and it's easily fixable with some sort of "feeding" system which relies on gravity or a pump to move the RO water over

2) Anything can be fixed with corrections, but the reality is most people would probably go on autopilot most of the time and don't monitor salinity very often, so the drift will depend upon how lazy one is and how much cross contamination there is. There could be tiny amounts, in which case yeah your skimmer pulling gunk might end up being a large salinity drift on your system, or there could be a situation like how I like things to go with my reservoirs and the drift would be closer to topping off with SW than FW.
 
sfsuphysics said:
This really only works if you use 100% of the salt water, and even then there might be some residual SW in the bottom of the container that doesn't come out so there would be a tiny amount of contamination. Now is it big? Probably not, but over any long enough time span even water at 1.001 will eventually start causing a salinity creep just from "FO" top off.

Now I don't know, maybe I'm weird in that I don't use all my SW at once, if I get low I say "hey time to refill"
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No, there is no contamination, and it still works.
The RODI water drips in through a float valve.
So your slightly-salty container fills up to the top, then the float valve stops flow.
Flow is off, and actually pressurized behind the valve, so no way to back contaminate.

The only problem - since new water has some salt in it, you do have to measure and test salinity as you mix it,
instead of simply dumping in the usual amount.
 
sfsuphysics said:
1) Well from what I gather "tee on output of freshwater" you essentially fill up both containers at the same time, or at the very least one full container of RO water, then turn the valve which will drain half of the water into the SW container as the levels equalize, then you fill up with RO water so both are completely full, ....
Click to expand...

I think I see the misunderstanding.
The water does not drain from RO container into SW container. (or back)
It only comes from RODI membrane and filters to both containers.
There is no direct connection between connection, and water cannot pass that way due to float valves.
 
xcaret said:
I have two 50g water barrels that are looking for a home and if you want to try a "continuous water change" system, I also have a Masterflex dual head pump.
I think if you are going to have a shed for water mix/change, go as big as possible with the container; not the size of a swimming pool.
Click to expand...
I might want that dual head pump. My current water exchange pumps are not doing so great.
 
rygh said:
I think I see the misunderstanding.
The water does not drain from RO container into SW container. (or back)
It only comes from RODI membrane and filters to both containers.
There is no direct connection between connection, and water cannot pass that way due to float valves.
Click to expand...
ah... a tee from the RO/DI water creating dohickey, not the RO/DI water container. Gotcha... yeah that could work too.
 
jccaclimber said:
Mario, I'm curious, what was the noise level on the Masterflex compared to other dosing pumps?

As for mixing, I personally like to T the RO in to both containers, but 95% of the time I leave the T to the salt container shut. This way I have a big container of fresh ready, but my salt container doesn't change salinity until I choose to refill it from the fresh container. If I ever need to fill both at the same time I have the option still. This is only useful if you don't mind keeping pre-mixed salt water on hand, which of course has upside and downsides.
Last time I set up a mixing station for someone I made it so that the volume of the salt container (at a mark, and minus the dead volume) was just the right amount of water to dump in 1 bag of salt mix and end up at 1.025. This works pretty well if you always buy a specific brand and bag size of salt. If I'd been thinking I also would have put 1.024 and 1.026 marks in the container for correcting salinity during a water change.
Also, put a transfer pump somewhere in the system. If you plumb one pump in to both tanks with shutoff valves you'll get slight cross contamination, but this really doesn't matter in most circumstances. Note, if you run a kalk system you will get some precipitation from this in your kalk container, so flush the line first if you do both.
The other benefit of the transfer pump, aside from filling jugs faster, is that you can put the outlet back in to the salt container. This way you can fill it with fresh, dump in your salt, then just come back in an hour when its all mixed up.
Click to expand...

The one I have is not silent as the DC/Digital drive; IMHO, compares in noise as many of the dossers out there IE Bubble Magus, BRS Dossers
 
sfsuphysics said:
ah... a tee from the RO/DI water creating dohickey, not the RO/DI water container. Gotcha... yeah that could work too.
Click to expand...

https://www.bulkreefsupply.com/3-way-ball-valve-with-john-guest-1-4-push-connect.html

This is the valve I used. Coming off the rodi unit I could divert the water from one side or the other or off in the middle. Then each reservoir had its own float valve that would shut it off when full. Typically I needed freshwater for the ato (I didn’t do water changes) so I would just turn it to that side and walk away. The next day I’d put it back in the middle. For sw I’d let it drain completely (or near completely) before doing the same and then adding salt until I reached 35 ppt.
 
I'm a bit unfamiliar with float valves as I don't use them because I also use a booster pump to up the pressure in my system. So while sure a float valve would work, my booster pump would continue to try and pump and something may get damaged.
 
sfsuphysics said:
I'm a bit unfamiliar with float valves as I don't use them because I also use a booster pump to up the pressure in my system. So while sure a float valve would work, my booster pump would continue to try and pump and something may get damaged.
Click to expand...

I have a booster too. The inline pressure switch cuts power to the booster at the same time the mechanical valve cuts the incoming water so that the wastewater line stops.
 
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