RODI Woes

[WindowMaker]

Alright, my RO system has been less than perfect to me over the past year and Im at the point where I may smash it if I cant get it where I want it. Im going to flood this with background details so that you may be able to help me out here.

MY system is a BRS 6 stage with the dual DI. I do have the filter monitor, pressure gauge and TDS meter as well. I have probably run 150 gallons through it at this point due to low water demands.

WATER SUPPLY

Currently my RO is hooked up with a t split under the sink, it is hooked up to cold water only. I am in an apartment building and my cold water comes in at city pressure which equates to about 30-35psi on a good day. The water is very cold and I feel this may be slowing the process. The hot water in the building is boosted after the boiler and boasts much higher pressures.

I have been trying to find a way to hook up both hot and cold under the sink and mixing the two. Would it be feasible to put a t split on the hot water and run both hot and cold into a Y fitting in the RO system? if this is feasible, should I put a valve on both hot and cold so that I can control the temperature going in? Does this make sense or am I crazy? Ive looked into mixing valves but they only appear to work at temperatures of 90+ which is way too high for the RO.

PRESSURE ISSUES

Lately I have been struggling to maintain even 10 psi. I have a good feeling this is due to clogged filters. I have changed the sediment filter without much luck in pressure, but I imagine after a year the carbon cartridges are about done too. I have ordered a full filter/DI kit as my di resin is just about exhausted as well. Hopefully this gets me back to my 25-30 PSI from before.




what do you guys think of my mixing idea? do you think it will work or am I head in the wrong direction?

[daplatapus]

Is there a reason you don't want to put in a booster pump on your RO/DI with a pressure cut off switch? That would be the best option if you can do it.
Something like this would work:
http://www.jlaquatics.com/phpstore/s..._ID=vt-rozbsts

or this:
http://www.bulkreefsupply.com/1-4-aq...-pump-kit.html

[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

[rhody605]

I got my booster pump from aquasafe out of b.c. A great investment. Under $100 shipped.

[hillegom]

As a lot of people are saying,
a booster pump is what you need..
RODI requires at least 60 psi to work properly