Tank cooler/RO-DI warmer

[Dalmerjd]

I have 600 gallons worth of mixed reefs. I have lots of halide lighting, which in turn means lots of extra heat and evaporation. I have been trying to figure out a way to make my RO/DI more efficient. I have been caught short a couple times when my water demand exceeds my RO units output. Without buying a larger or second unit, I needed more water. I have been told that water coming into the RO unit should be 75-80 degrees F for optimum performance.
To achieve this I bought 60 feet of 3/8" nylon tubing. I tied this tubing inline to my RO units water supply. I then submerged the tubing into my sump. Doing this raised my RO water supply temp from 64 deg to 78 deg. My RO water output increased about 30% with little increase to my waste water output. Since the water flow is relatively slow, I have achieved 100% heat transfer. An added bonus for this DIY project was extra cooling for my system. Some days when the RO unit is running all day, my cooling fans do not run at all.
This was the best mod I have done to date. I got more RO water being made at higher efficiency. Free cooling for the system which in turn requires less evaporation cooling. Less evaporation cooling in turn puts a lower demand on my RO unit.
This has been the only win-win-win project I have ever done. All at a cost of $25 and 20 minutes of time.
Parts required are tubing and one compression fitting. Be sure to get the compression fitting with the inserts or you will crush the tubing resulting in leakage.
I thought this worth sharing.

Jeff

[laugh]

Somehow this just makes sense to me. I am going to upgrade to halides and I have well water that comes in very cold. I just might end up using something like this as well.

[scottwhitson]

Great idea if I ever get my sump moved to the basement where my RO/DI is this will definently be something that I do.

[kcress]

Yep the hotter the better for RO up to 90F.

The only down side is if your feed hose ever springs a leak... You will poison your sump/tanks. So, you should keep in mind that that hose has high pressure in it and monitor its health on a regular basis. If any doubt ever comes to mind replace it!

[Dalmerjd]

<a href=showthread.php?s=&postid=15014823#post15014823 target=_blank>Originally posted</a> by kcress
Yep the hotter the better for RO up to 90F.

The only down side is if your feed hose ever springs a leak... You will poison your sump/tanks. So, you should keep in mind that that hose has high pressure in it and monitor its health on a regular basis. If any doubt ever comes to mind replace it!


Quite true. I plan to install a high level switch in my sump and a solenoid on the supply line before the tank. If the level goes high my Profilux will close the solenoid and minimize contamination.

[kcress]

Good plan! Neat trick to BTW.

[Mike31154]

I don't have a sump yet, so I simply coil an extra length of RO/DI feed line into a bucket of warm water and use a heater to keep it warm.

[redfishsc]

Man, Jeff that is one of the most witty things I've heard of around here. Bravo.


I don't know how you have your RO unit plumbed, but if you are using a pressure pump to drive it, you might consider putting the pressure pump on the side of the flow coming OUT of the tank, so that the hose coiled in the tank doesn't have any more pressure on it than ambient source pressure.


Not sure if that's an option or not though, and not sure how you'd rig that up.

[Dalmerjd]

Hi redfishsc, at the moment I am not using a booster pump. I might decide to use one in the future though.
Here's how the plumbing goes.
I disconnected my original 3/8" tubing from my water source(JG type fitting)
I installed one end of the 60' of the new tubing into the JG style fitting.
There are no cuts made to the 60' of tubing I bought.
I coiled up about 50' of the 60' of tubing I bought and submerged it in my sump, at this point it's empty so it wanted to float until I charged the line with water.
I connected the other end of the tubing I bought to the compression fitting.
I hooked up my original tubing, that I disconnected earlier, to the other side of the compression fitting.
Did a leak test and, viola, done.
Easy, simple, cheap and effective!
Gotta like it!
However, like kcress says, watchout for leaks.
The tubing I bought is rated to 150 psig @ 160 deg F and is potable.
A booster pump can very easily be added on the downstream side of the tank for more pressure should you need it.
This can be adapted to any size tubing or style of hookup with the appropriate parts.

[Dalmerjd]

Before I did this mod it took 96 hours to make 75 gallons of water using a 50 gpd RO unit.
Now it takes 60 hours to make the same 75 gallons of water.
So, overall efficency of 60%. 1.25 gallons per hour or 30 gallons per day out of a 50 gallons per day RO unit.
Next mod...a booster pump. Currently my well pump pressure runs 35-65 psig. Nowhere near the 90 psig recommmended.

[therealfatman]

Sorta out of place in this thread but for those wondering: RO membrane testing parameters use 75 to 77 degrees F as a standard, however output increases at higher temperature. The TFM design maximum high temperature is actually quite a bit higher than 90 degrees.

As posted online:
Maximum operating temperature 113° F (45° C)
Applied Membranes (Residential and Commercial Models)

To actually calculate the difference in water output see this article and the supplied simple equation.

http://www.watertreatmentguide.com/temperature_correction.htm

Remember even though you produce more water you also proportionally waste more water. Tigher temperatures than design ratings increase performance (output) usually not efficiency. Nope no free lunch here either.

I use a small commercial unit with mixed flow water (hot and cold water mixed) as my required iflow intake is larger than my cold water line supplies. My water input temperature is 110 degrees typically and my membranes last at least two years. I change out at two years whether they need it or not. I can get away with that economically as my landlord payings for heating costs and my hot water is supplied by the heating boiler.

[Dalmerjd]

Hi there therealfatman, do you know how much pressure is too much for these membranes? This spec I can't find.

[BeanAnimal]

<a href=showthread.php?s=&postid=15019495#post15019495 target=_blank>Originally posted</a> by Mike31154
I don't have a sump yet, so I simply coil an extra length of RO/DI feed line into a bucket of warm water and use a heater to keep it warm.

That may increase the output if time is a contraint, but it is not at all cost effective.

[BeanAnimal]

<a href=showthread.php?s=&postid=15024165#post15024165 target=_blank>Originally posted</a> by Dalmerjd
Hi there therealfatman, do you know how much pressure is too much for these membranes? This spec I can't find.

75 PSI is common target. 90 PSI is acceptable in some well built units. When you move past that, you start running into other problems like bypassing in the housing seals and stress on the fittings and housings etc. In other words, the max pressure rating of the membrane itself is not the limiting factor in most cases.

[Plankt0s]

This should be one for everyones brain box. Thanks

[arctictwist]

Wow, Great Idea! I wish i didnt have my "water making station" already!

[Buckeye Hydro]

Max operating pressure for the most widely used membrane out there, the 75 gpd Filmtec, is 300 psi.

What Bean mentioned above is exactly right. There are typically other components in these residential units with a max operating pressure of 100 psi. Our 90 psi recommendation is intended to leave a ~10% safety margin.

If you are going to heat your feedwater as Jeff did, make sure you use 3/8 or larger tubing. Once you get over about 25 feet with 1/4" tubing the pressure lass defeats the purpose.

Russ

[therealfatman]

Thanks BFS. The operating pressure limit is usually controlled by the components not the membrane. The next step up in RO filter systems is the small 350 gpd are less filters and they usually have a recommended maximum of operating pressure of 200 to 250 psi and that is due to component parts. They still use plastic fittings, larger but still plastic, but the housings are either stainless steel or a heavier plastic and flow restricters are replaced with valves and diverter valves etc. Plus they use their own pumps to supply water pressure. There are membranes made to operate with huge pressures, like ten fold what would be used in a home. The small commercial filters are more efficient and produce cheaper water, but they can easily cost 10 times as much or more while only producing two to four times as much water. The RO membranes are usually 20" or longer and 2" or larger in diameter.