[Stephen burton]

Hi guys, I have a 300gpd unit my water is 380 ish at home, after the membrane it comes out about 0.34 for some reason after it goes through the di chamber it comes out at 003-007 it's not that old about 6 months and had very light use and it always use to come out at 000 any ideas please

[Don Kee]

How big is your D.I?
& how many litres a week do you produce?

[Smurf]

Are you aware of tds creep and do you backflush the membranes?

[Stephen burton]

About 800 litres a week most weeks sometimes less di is little 700 l plastic chamber

And no never heard of tds creep and back flush of membrane

[Don Kee]

700L or 700ml?

I'm assuming 700ml as otherwise its one hell of a D.I,

your resin is spent

[Afterglow Window Cleaners]

Also, when did you last change the pre filters?

[Stephen burton]

It's 700ml sorry, haven't changed pre filters but the water is exactly the same reading after membrane as it was when it was new and the resin is brand new so everything is working how it should be until it's hits the di

[Smurf]

Here is a vid that may help you understand tds creep etc.
https://www.youtube.com/watch?v=x6f07WzT2Ng

[Afterglow Window Cleaners]

If the water is coming out of the membrane at the same TDS as before then that only leaves the DI stage.

Did you pack the resin into the cartridge and replace the sponges to stop the resin escaping?

Also, if your water is coming out of the membrane at 34ppm then you really do need to either change the membranes or increase your water pressure through them as you will use a load of resin quickly

[Stephen burton]

Yeah I pack it down lots my pressure is low and I'm waiting for a booster pump, I just don't understand how it has changed all of a sudden, if it was coming out of the membrane more then before then I would buy new membrane, do I buy a new di chamber and see if that is the problem

[SeanK]

With a 7 litre DI vessel and your water 34 after the R.O. then you have done well to get six months, you need new
resin and a booster to get your RO tds lower but new resin should do for now.

[Stephen burton]

I have new resin in the cartridge today, it doesn't last that long either, probably about 400-500 litres before I change it and i can't complain as I know it's due to low pressure of only 40 psi

[Spruce]

380 in and 34 out.

Membranes are only working at 89.5% rejection rate. A RoMan type r/o should be working at between 97 and 98%. So your rejection rate should be between 10 and 12.

Maybe water pressure has something to do with it, but I if you haven't changed prefilters, then chlorine could have begun to destroy the membranes.

I would connect each membrane housing up to your prefilters and check the output after its been running for 5 minutes or so. I could be one faulty membrane that's causing the problem. If they are all similar readings then the faulty is either membrane or pressure or both.

[SeanK]

I have new resin in the cartridge today, it doesn't last that long either, probably about 400-500 litres before I change it and i can't complain as I know it's due to low pressure of only 40 psi

With a TDS of 34 you should be getting more than 400-500lts per 7 litres of resin, something's wrong somewhere its either
TDS creep like Smurf said or your buying bad resin.

[jk999]

Which would perform better   one eleven litre di or two four and a half litre di 's?

[jk999]

?

[slap bash]

If you do not use a booster pump on your ro your water will have a high degree of waste water and  you R O will not perform well as the membrane become older the water will not be able to penetrate the membrane as the calcium will build up on the membrane surface and deliver a low quality result. Flushing does help but if the water pressure is too low it will not last.