RODI Woes

[mike31154]

Mixing hot/cold is a bad idea. Since your input pressure with the cold is very low, consider a booster pump. They're readily available for RO systems. You need somewhere around 60 psi for a membrane to start working effiiciently. 150 gallons total throughput is not very much & your filters/DI media should be nowhere near exhausted.

My experience is that colder water, while slowing production down a little, actually results in 0 TDS output after my RO stage after running for about 5 minutes. This is with water at 8 to 10 degrees C. In the summer, when the water temperature coming into my house ranges from 10 to 15 degrees C, the membrane manages a TDS of 1. I'm fortunate to have access to the pressure regulating valve in my home's plumbing, so I've adjusted it to provide 100 psi to my RODI. This higher pressure allows me to produce close to the rated gpd output from the 75gpd membrane at the colder water temperatures. Being in an apartment, it's unlikely that you have access to the pressure regulating valve, so that leaves you with the option I already mentioned, a booster pump. I suppose you could always complain about low pressure to the apartment superintendent, maybe they can do something about it.

[rstar]

Im going to piggy back on this thread as I too believe I am having pressure issues, ordered a psi gauge last week, just wondering where in line I need to install it to test pressure?

[ckmullin]

booster pump seems to be lacking

http://www.maxwaterflow.com/Booster-Pumps_c_146.html might be of help

got my 6 stage unit from them and pleased

[mike31154]

Originally Posted by rstar

Im going to piggy back on this thread as I too believe I am having pressure issues, ordered a psi gauge last week, just wondering where in line I need to install it to test pressure?

Most RODI systems that come with a pressure gauge recommend installation before the RO membrane (after the pre-filter & carbon stages). I've taken it a step further & installed two pressure gauges, one as per above recommendation & another at the RODI system input, measuring house pressure. This allows me to keep track of a pressure differential between the two & is one of the best indicators of when your pre-filter stages need replacement. Using simple math, when the pressure differential reading between the two begins to rise 3 to 4 psi, it's pretty obvious the sediment filters are gumming up. I keep track of the numbers on an Excel spreadsheet. Although the poly pre-filters aren't that costly, it's still more cost effective & less of a hassle to change them when truly required rather than on some arbitrary time based schedule.

I purchased both gauges at Princess Auto. Liquid filled, good quality for just under $20. No need to order something through the mail when it's available for competitive price locally.

[chewie]

To compensate for cold water in the winter i got about 20 feet of water line wraped around the inside a 5gallon bucket then filled the bucket with water and put a heater in it. So the water goes from the water source, warms up from the warm bucket water then into my rodi unit. Seems to help a bit.

[WindowMaker]

On what chewy said, I could probably just wrap the water feed line around the hot water pipe under the sink.

All that being said. My carbon and sediment replacements as well as fresh batch of DI resin and my pressure has takes a substantial step up. Im still sitting at 35psi, but thats a whole lot better than the 10 it was before.

Booster pump is on the "things to buy" list

[lastlight]

if you consider how fast the water is moving into your unit (waste + clean) it's actually moving really fast. the plastic tubing isn't going to really let the heat transfer very well either. i'm not saying the bucket trick doesn't help but i'm guessing it would be so miniscule and probably not worth the cost of running the heater.

you should test the temp of reg output and then heat the bucket up and compare i am curious =)

[hillegom]

Just in case your to do list is waiting for appropriate funds, consider this:

http://filterdirect.com/index.php?cP...89aaa86f823695

[mike31154]

Originally Posted by lastlight

if you consider how fast the water is moving into your unit (waste + clean) it's actually moving really fast. the plastic tubing isn't going to really let the heat transfer very well either. i'm not saying the bucket trick doesn't help but i'm guessing it would be so miniscule and probably not worth the cost of running the heater.

you should test the temp of reg output and then heat the bucket up and compare i am curious =)

I tried this scenario (coil of tubing in bucket with heater) for a while too & found it wasn't worth the effort. Increasing the pressure is the way to go.