RO Supply Line --> Pressure Return?

[coreytrv]

I've seen a lot of RO setups where the unit is plumbed directly into a tank that is upstairs, or a fair distance away...BUT, does anyone know if it's possible to use an existing pressurized return, and plumb directly into that feed?

I'm trying to avoid using an empty 1" pipe that's 35' long to fill with RO water just to top of the DT Tank, as it'll just sit there flooded. I also need to add water directly to the DT, rather than the sump.

So I'd like to plumb the RO supply line directly into the pressurized return from my closed loop canister filter. Anyone know if this can work? thinking back pressure issues?

 

[Sisterlimonpot]

Are you saying that you want to plumb in directly from your rodi outlet line?

What's the pressure on the return line? Usually closed loops operate with very little pressure differential on either side of the pump. It's mostly pressure of the weight of the water in the tank. But if you use bernoulli's principle and set up the rodi line to a venturi then back pressure wouldn't be an issue while the closed loop pump is running.

There are a few concerns to plumbing rodi outlet directly to the tabk. TDS creep being the biggest. Turning the rodi on and off based on evaporation is going to negate the use of rodi and will burn through your DI resin rather quickly.

The better idea is to set up an appropriate sized ATO container next to the sump and fill that up with rodi when it gets close to empty. Then have a pump draw from that when top off water is called for.

The traditional way of doing things is popular for a reason. Hehe

 

[coreytrv]

Are you saying that you want to plumb in directly from your rodi outlet line?

Yes

What's the pressure on the return line?

About 20 psi

Usually closed loops operate with very little pressure differential on either side of the pump. It's mostly pressure of the weight of the water in the tank. But if you use bernoulli's principle and set up the rodi line to a venturi then back pressure wouldn't be an issue while the closed loop pump is running.

How would I do that? Wouldn't that require adding restriction to the line somewhere?

There are a few concerns to plumbing rodi outlet directly to the tabk. TDS creep being the biggest. Turning the rodi on and off based on evaporation is going to negate the use of rodi and will burn through your DI resin rather quickly.

The better idea is to set up an appropriate sized ATO container next to the sump and fill that up with rodi when it gets close to empty. Then have a pump draw from that when top off water is called for.

I've read similar concerns from the forum, asked the guys at BRS about it, this was their response...you think it's a fairly significant concern?

(11:47:27 AM) Matt (Bulk Reef Supply): for that run, and to not have a really over powered pump, topping off from to RO unit may be the best!
(11:48:43 AM) corey: I saw a BRS short on that- you don't find using RODI to top off tank directly, rather than res. shortens rodi filter media lifespan?
(11:50:27 AM) Matt (Bulk Reef Supply): It can but not enough
(11:50:33 AM) Matt (Bulk Reef Supply): we do it on all the bi tanks here!

The traditional way of doing things is popular for a reason. Hehe

Thanks for the responses!

 

[KStatefan]

With the 20 psi at you return if you hooked up your RODI there it would lower your effective pressure at the membrane 20 psi also. You could set up the tank next to where you want to pump the water in then pump it into your return. It would not have to be a very big tank ie 5 gallon water jug.

 

[DCR]

Higher backpressure on the permeate (return) will reduce the TDS removal efficiency of the RO for a given supply pressure and reject rate. You should try to minimize the backpressure on the permeate side of the membrane.

 

[Sisterlimonpot]

I've read similar concerns from the forum, asked the guys at BRS about it, this was their response...you think it's a fairly significant concern?

(11:47:27 AM) Matt (Bulk Reef Supply): for that run, and to not have a really over powered pump, topping off from to RO unit may be the best!
(11:48:43 AM) corey: I saw a BRS short on that- you don't find using RODI to top off tank directly, rather than res. shortens rodi filter media lifespan?
(11:50:27 AM) Matt (Bulk Reef Supply): It can but not enough
(11:50:33 AM) Matt (Bulk Reef Supply): we do it on all the bi tanks here!

I don't know who Matt is, but he either misunderstood your question, or shouldn't be offering that advice.

You also have to consider you're asking a representative of a company who's chief goal is to sell you stuff.

Come to think of it, of course they'd recommend that, because it means you're going to be purchasing more di resin.

TDS creep is generally something you want to try and prevent.

How would I do that? Wouldn't that require adding restriction to the line somewhere?

Pretty much. Going this route raises a lot of other concerns. What effect does that negative pressure have on the rodi system when it's not operating? You'd probably want to incorporate a shut off solenoid.

About 20 psi

Is this a guess? How did you determine that?

 

[coreytrv]

I don't know who Matt is, but he either misunderstood your question, or shouldn't be offering that advice.

You also have to consider you're asking a representative of a company who's chief goal is to sell you stuff.

Come to think of it, of course they'd recommend that, because it means you're going to be purchasing more di resin.

lol, good point, they would love us reefers out here burning through DI resin

TDS creep is generally something you want to try and prevent.



Pretty much. Going this route raises a lot of other concerns. What effect does that negative pressure have on the rodi system when it's not operating? You'd probably want to incorporate a shut off solenoid.


Is this a guess? How did you determine that?

I looked at a chart for PSI and flow rates, but that was probably a very rough guestimate.

Sounds like I should use an ATO to fill my RODI tank, and then just use a pump to feed into that return line, then pressure wouldn't really be an issue?