Ro pressure tank as auto topoff??

I have no running water source to my tank. My ro unit Is on the other side of the house. So I was wondering if I put a 5-10 gallon ro pressure tank next to my tank and ran a float valve in my tank then I could fill up the tank every week and not worry about over flow because my sump can hold well over 15 gallons of over flow. Can a ro tank hold or/di water?

 

It's easier to use a 5 gal bucket with a snap-on lid with a small pump in it. We use a John Guest adapter on the pump output and 1/4" poly RO/DI type tubing thru a small hole in the bucket lid. I also added a John Guest Tee above the bucket's water line to act as a siphon break since the end is submerged in the sump.

Just plug your pump into the float valve and away you go.

 

+1

Just a couple of additional notes:

1) Since your overflow keeps the tank level constant, the float switch will need to be in the sump where the variation occurs.

2) You'll want to ensure that it's fail-safe. While the sump may hold the extra water, that much at once would drop your SG and possibly kill your corals and inverts (if not the fish, as well).

 

+1 on using a pump, tubing, and a 5 gal pail.

That's what I do.

 

But then I would need more electronics. And a pump. Just one more thing to break of go wrong.
And I feel ato are unreliable

 

I guess I haven't seen one, so I'm not sure how you would make a pressure tank work? How were you thinking of doing it? What do you mean by "RO tank"?

 

So a ro pressure tank holds water between half of the tank and the rubber liner. On the other side of the rubber liner there is 80-100psi of air so when the valve or float would open it would automatically push the water into the tank. When the valve closes it would stop draining the tank.

 

You'd fill the tank and transport it across the house or run an RO line to it?

I guess it could work, but you would have to go lower than 80-100 psi behind the bladder. My guess is you can set the tank pressure down around 10-15 pounds. The maximum feed pressure to the RO's is usually around 80 psi. Your permeate (clean water) pressure will be quite a bit lower than that by the time you figure in pressure drop across the membrane.

The downside to that will be a shorter DI resin cartridge life. The spiral wound TFC composite membranes aren't really meant to run with much back pressure on the permeate side. If you have significant back pressure (say running it up to 40-50 pounds filling a pressure tank), you decrease the pressure difference between the feed and permeate. This will lower your rejection and mean that your DI resin will have to remove more dissolved solids. In addition, if you suddenly go from an 80 psi feed to no feed pressure, you can delaminate a spiral wound membrane as the clean water tries to rush backwards through the membrane.

Not saying it can't be done, but it seems like a much more expensive route than a 5 gallon pail and a WalMart power head. You could replace the powerhead every 6 months regardless of whether or not it failed and be money ahead.

If you do go the tank route though, I would make sure to do these things:

1) Set your bladder pressure as low as possible
2) Do not go over a 30-35 psi back pressure on your RO when filling the tank. You can try going higher, but keep an eye on how fast your DI resin gets depleted.
3) Make sure you have a way to relieve the feed pressure slowly to avoid any hammering, which could lead to delamination and shorter membrane life.

Good luck!

 

Well great I did not know any off that about my ro system and am still kinda confused. But with that worry I guess I will go the bucket route.

So with the Chepo power head do I just run it straight to a float valve in the tank and just let it run???

 

I'm sure there are better systems out there, but I started with this. Bought the float off E-Bay for $6.00. I will probably upgrade in the future.

DIY Auto Top Off System - YouTube

It's been fool proof for 10 months. You just have to be careful to properly seal the splices just in case they do get any water splashed on them. I used a "liquid" electrical tape and then actual electrical tape.

If splicing into electrical wires is not your thing, I've seen people talking about autotopoff.com in the forums.

Good luck!