RO Help

[cfmx]

Ok so what am I doing wrong??!!
We have a 5 stage RO/DI unit that seems to do a great job but for a very little period of time.
For instance about 2 months ago we just replaced all filters including the membrane our water was testing out at 0 after a couple of uses it steadly increases.
Today I checked the and the ppm 32. I changed out 10 micron, 5 micron sediment filter, 1 micron carbon filter and back flushed the membrane unit. Then ran it for a little bit and rechecked the ppm (1). After making 40 gallons of water the ppm is now 6.
I checked our tap water which reads at 238 ppm.
What is wrong.

[a2fire2i]

Do you know what your TDS before going into the DI is? What are you using to check the TDS? Inline meter? Handheld meter?

[InADream]

How long have you had the membrane? I had similar issues and replaced the membrane, now is well.. also at any point did the membrane become dry.

Dream

[Northtampatang]

And you mentioned changing the prefilters, but how old is your DI resin.

[cfmx]

a2fire2i - I will have to check the ppm prior to going to di. I have a handheld meter.

InADream - the membrane, di resin and all filters where replaced 2 months ago. Water tested at 0 ppm then but has increased to 32 ppm. I make about 50 gallons every other week. To make sure the filters don't dry out I h ave placed 3 off values on the unit to keep water from draining out (water going in, waste water, good water).

Northtampatang - 2 months old

[a2fire2i]

What do you put your water in to test the TDS? I have heard of stuff from the container fouling the sample as it can raise the TDS number. Also, did you buy bulk DI resin? If so, how was it stored? If not in a sealed bag, it can pull stuff out of the air and exhaust it..

[Tampa Aquarium Service]

When you test your TDS how long are you allowing the unit to run before you test? When the system shuts down there is quite a bit of fowling that happens to the water left in the filters and membrane. You need to run the system for a bit to allow it to flush out the skunky water before you test it anywhere along the system.

[drosen]

Okay so there are a few effective ways to run RO/DI fiters but what I have found is that cartridge selection and order can have a huge impact on your performance anf life (or fouling) of your membrane.

For example many people place the 1 micron sediment filter first only to follow it with a GAC filter. Problem is dust from the filter will clog the membrane and even kill it - back wash or not!

I would suggest one of two combinations:

GAC - Sediment - Carbon Block - Membrane - DI

Then use your TDS on either side of your DI to know when it is ehausted

Another way to go which is my new setup is to use:

Sediment - Carbon Block - Carbon Block - Membrane - DI

There are some good blocks on the market that have no dust and last a long time.

There is an excelelnt resource I found at:

http://www.thefilterguys.biz/

These guys have great prices and very friendly and will troubleshoot with you.

[drosen]

One more thought - filter selection relative to particulate size is also important. Given your current cartridges a 1 micron sediment would improve your efficiency - but two sediments prior to a carbon might be the issue -

Are you in an area where you are prepping well water or city water?

[bigt0706]

also what is your water pressure

[cfmx]

We did buy buld di resin that was stored in a plastic bag sealed w/ tight w/ a rubber band.
As far as testing the water w/ tds meter I normally let it run for 5 - 10 mins and then I also like to test the last bit of water I made to see how much it has increased. I normally collect the water in a small cup. I could try a paper cup next time.
I'm not sure what our water pressure is.
Maybe I will see if the filterguys can help.