RO unit affected by water temp?

C

Cheech

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Jan 13, 2000
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I have an old RO unit, (easily 7 years old, hasn't been used for about 6 yrs)

So I lent it to a friend of mine cause I purchased a new one and he's setting up a new tank.

The chambers of the RO unit I lent him have stagnant water that has been there for years, so I asked him to setup the unit, see how it goes, test the water, and if it's not par, to change the cartridges.

He installed the system and the good water was pissing out, much faster than it should. he brought the unit to the lfs and the employee told him that the probable cause was the fact that the water going into the unit is freezing cold, the unit isn't used at its full potential and this should be the reason why it's pissing out. (it's been freaken cold here lately, so the water is colder than usual).

Anyway, personally, I'd think the problem was the filters and not necessarily the temp. of the water.. I find it hard to believe that temp. would affect the overal usage of the RO unit to that point.

Anyone ever heard of this?
 
I know all RO units do have an optimal running water temp to be effective as per the manufacturers instructions..even so, that is to get proper ro unit usage. If you put colderwater through, i would imagine the output would be the same, prob just with a higher TDS....I am only surmising here though...

AS the following D&D ro unit description...

D & D Reverse Osmosis Units
New Reverse Osmosis Units from D & D Aquarium Solutions

Twin pod (carbon and sediment filters), TFC membrane, tap connectors, adaptors, and hose.

Ready to use once connected to water supply

AP50 : 50 US gals per day (Approx 40 UK gallons per day at full mains pressure at 16 deg C min)

AP75 : 75 US gals per day (Approx 60 UK gallons per day at full mains pressure at 16 deg C min)

AP150 : 150 US gals per day (Approx 125 UK gallons per day at full mains pressure at 16 deg C min)
Click to expand...
 
Generally an RO membrane GPD is rated at 70 degrees F or thereabouts. Colder water will slow production through the membrane (not sure why...due to higher density at colder temperatures?) If the water was coming out faster, I would assume its ap problem with the membrane, not a temperature issue. What was the rate of rejection water? That should give you a good clue as to the quality of RO water the unit was producing.
 
Thank you for the responses. I had no idea water temp. affected the outcome.

Sploke, I'll ask him to check the flow in comparison with the bad water and see what he says.

I also think it's a filter issue (the fast flow) .. he'll be running it with warmer water tonight to see if anything changes.
 
Check the flow restrictor to be sure there is some flow from the waste line as well.
If the membrane dried out from being in storage for so long, it may need to be replaced as well. It might be damaged to the extent where water just flows right through. Typically the colder water slows the process...

Also make sure he is using the water from the output, and not the waste line from the unit.
 
If it sat for years, all of the pre-filters and the RO membrane should definitely be replaced. While having it all apart, I'd also clean it with a mild bleach solution, rinse it out really well, and replace all of the tubing. It only takes a very small film of bacteria to significantly reduce flow through the tubing.
 
A lot of good advice so far.

To sum it up:

You're supposed to change the pre filters twice a year for bacterial reasons. I don't - letting them go about two years, but I certainly would change them immediately before using them after several years.

2) If a membrane gets dry it is completely toast!

3) People often get the (product) and the (brine) outlets confused. The product which is what you want should come out about 1/4 as fast as the brine or discarded stream. (which I do laundry with).

4) Temperature GREATLY affects RO production. As mentioned, the standard is about 71F water. If you feed your RO 40F water you will get less than half the flow of product! This is why municipal RO systems always try to cozy up to power plants. Even a few degrees makes a huge impact.

5) A seven year old membrane should not be used at all. They grow bacteria and when they fail put out a very fine flaky debris that is hard to see but could affect the use in a negative way. Even the most cared for membrane starts to decompose at about 6+ years, let alone one not cared for.
 
Luckily, I don't really have to worry about bacteria, since I use a .2 micron pleated sediment cartridge. One good reason to invest in these. I still recommend a good sterilization whenever membranes are changed, however.
 
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