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View Full Version : Cant get TDS below 15-20


amcvay1979
02/10/2016, 04:10 PM
Hello, I've been having issues w/my RODI system. When brand new (less than a year) the TDS after the membrane was typically 4 or 5. It crept up gradually to 20-35 so I've changed almost every part of my sytem. New filters (sediment, 2 x carbon blocks) and even a new Dow Filmtec membrane about 3-4 months ago.

My incoming TDS is 120-140 and that's fed to my RODI after a Whirlpool whole house regenerating filter and a softener. The temp of my water right now is really cold, probably 50-60 degrees (I can verify this and get an exact number) and after balancing my product/waste ratio to 1:4 my pressure is around 45-50 psi. My DI resin takes it down to zero and that's fine, but I'm going through it much quicker than I need to.

I've thought about bumping the pressure up by running 1/2 inch hose from my feed water to the RO/DI hoping to increase pressure, not much I can do about the temp in Feb in the midwest though. Every filter on my unit is less than 4 months old. When I replaced the membrane TDS were again back to 4 and this is where I'd like to keep it.

Spent carbon blocks? Fried membrane (again?), should I feed my RO before it goes to the whole house or softener? I'm at loss for how this thing won't keep performing.

vhuang168
02/10/2016, 08:01 PM
Do you flush your membrane before each use?

amcvay1979
02/10/2016, 08:36 PM
It's on constantly attached to a float valve for ATO, so I don't flush and make large batches

amcvay1979
02/10/2016, 08:44 PM
I have flushed it and when I do it still doesn't get below 15 when I run it for an hour non stop.

azjohnny
02/10/2016, 09:01 PM
To increase water pressure you will need a booster pump not sincreasing the feed water pipe size.

If you have Cholramines that can kill your membrane and elevated CO2 levels will cause you to go through DI quickly


Cold water will give you lower TDS but decrease production

Try getting a hold of Spectrapure directly, they will help you even if it isn't their product

vhuang168
02/10/2016, 09:48 PM
My tap tds is 280-350. It runs through a softener before going to the rodi. TDS is after softener.

If I don't flush, tds after membrane jumps to 30-70. If I flush for 10mins, it will drop to 0-2. My pressure is 60psi.