Head Pressure and RO/DI Production

tigÃ©21v · Feb 8, 2017

I recently made some changes to my setup. I have two separate units, a 4 stage RO unit, and a MaxCap (dual stage) DI. It used to be set up inline, the two units next to each other, with the water storage container located below the DI "out" water line. Due to space constraints with the change made to other areas of the fish room, I mounted the the units above/below each other- the RO unit is now below the DI unit, maybe 12-15". And now, the DI "out" water line feeds into a container that is about 6" higher that the DI unit.
I've noticed that it seems my water production has dropped off considerably, probably a third or better. The production usually drops some in the winter (our tap water is in the 40's), but I don't recall it being this much of a drop.
So it got me to thinking.... Would the head pressure affect the water production? I assumed it wouldn't. The height difference is maybe a couple of feet tops, and I have really good water pressure (90+psi) But now I'm not so sure.
Any help would be appreciated.

Joeganja · Feb 8, 2017

Well the recommended pressure is around 50-60psi depending on your unit. Mine gets a 60si and I've never seen it reach 90+ so your lucky. And if you think about it the more turns and tubing you have the slower the pressure will be by the time it gets to the 5th stage. Sure it'll be 90+ psi going into your rodi unit but when it leaves it probably drops significantly

Opus · Feb 8, 2017

Why don't you take the line going to the DI and run it to a temp storage container and run the unit for awhile and see if production goes back up to what you expected. If it does, then it would seem the DI setup is the issue.

tigÃ©21v · Feb 9, 2017

Opus said:
Why don't you take the line going to the DI and run it to a temp storage container and run the unit for awhile and see if production goes back up to what you expected. If it does, then it would seem the DI setup is the issue.

That's what I was thinking about doing the next time I need to make water.

AZDesertRat · Feb 9, 2017

Makes no measurable difference. 2.31 vertical feet equals a 1 psi drop in pressure is all or for every 1 foot vertical change it drops 0.433 psi.
Its probably the temperature which has a huge effect on production.
With a 75 GPD membrane you can expect around 68 GPD at 90 psi and 40 degree water temp. At 60 degrees that jumps to 104 GPD. I would live with what you have if its at all close to the 68 GPD in winter months. Colder water actually treats better and your DI will last longer so warming the water would be a step backwards.

tigÃ©21v · Feb 9, 2017

I'm getting around 50 gpd right now.
More than enough to meet my current needs.
Just want to be sure I am not sending more waste water down the drain than I need to .