[Ken]

Changed my RO and DI filters today (Pentair PRF-RO and standard 8 or 11 litre DI pressure vessel ). Treated myself to a brand new TDS meter from Gapswater when I ordered the RO filter.

TDS reading from the tap was 200. Reading after going through the RO was 30. Reading from the brush head after going through the DI was 35ppm. Obviously this is not great so I:

(1) checked what I was getting before the water went through my microbore and it was 35ppm.
(2) checked what I was getting straight from the DI and it was 35ppm.
(3) checked what I was getting between the pump and the DI vessel and it's 35ppm!

So either the TDS meter is stuck (but it was reading ok earlier) or I've got a problem somewhere.
I would have thought that if there was some impurity in the system then the DI would deal with it anyway.

Any helpful suggestions of what I could check next are gratefully received.

[lal]

Changed my RO and DI filters today (Pentair PRF-RO and standard 8 or 11 litre DI pressure vessel ). Treated myself to a brand new TDS meter from Gapswater when I ordered the RO filter.

TDS reading from the tap was 200. Reading after going through the RO was 30. Reading from the brush head after going through the DI was 35ppm. Obviously this is not great so I:

(1) checked what I was getting before the water went through my microbore and it was 35ppm.
(2) checked what I was getting straight from the DI and it was 35ppm.
(3) checked what I was getting between the pump and the DI vessel and it's 35ppm!

So either the TDS meter is stuck (but it was reading ok earlier) or I've got a problem somewhere.
I would have thought that if there was some impurity in the system then the DI would deal with it anyway.

Any helpful suggestions of what I could check next are gratefully received.

Hi Ken, did you give the system a good Back Flush after changing the Ro & Di filters.

[Frankybadboy]

30 out of ro the 35 after di i say you got di connected around the wrong way or you havent pushed the riser tube up right inside

[Ken]

Lal, I don't think the Pentair PRF-RO  needs flushing. I just unscrew the three housings and insert three new filters. The reading out of the RO was 30ish ppm so I think that's ok. It seems to be the DI that's the problem.

FrankyBB, I wondered about the riser tube so went out this morning and took the DI apart. The in/out are connected correctly and I checked that the riser tube was inserted as far as it would go. I ran the pump for ten minutes to flush it through but still getting the same readings.
I checked the TDS meter to make sure it wasn't stuck, our tap water is 200-220, and some filtered water that my wife likes for her tea was 185, so I think the meter is ok.
Could it be stale resin? It was the last in the bag, but was stored in a sealed container.
Any other thoughts before I have to bite the bullet and buy a new DI vessel?

[Stoots]

Ok so tap TDS is 200, after R.O is 30, so we know the R.O is working, albeit poorly...

Heres an idea, get an empty pop bottle, screw the lid on.... drill a hole in the lid and the base. Make one hole just big enough to force you tubing coming from the R.O into.

Fill the bottle to the brim with your resin, turn the R.O on

then out the other hole of the pop bottle should come pure water, if it doesnt alter the R.O tds then resin must be shot.

If it does the D.I is faulty somewhere

if you have some fresh resin try that either in the pop bottle or the vessel before concluding the vessel is at fault

process of elimination old lad

[Don Kee]

Firstly, 30ppm after RO from an input TDS of 200 is awful.

You should be getting at a minimum a 95% filter rate, so your TDS should be closer to 10ppm not 30ppm.
Seeing as you’ve put new membranes in, it should be even better than 10ppm to be honest.

Secondly, I would try fresh resin first before you start buying new DI’s.
If for what ever reason the resin you’ve put in had gone “off”, then it could be just as simple as needing new resin. (I think you said it was the dregs of a bag you’ve just used?)

Also if you flushed your membrane for a bit (which you should from new) but you connected the DI, the high ppm that would have run through the resin and spent it.

So I’d look at that new membrane first to improve that outgoing TDS and buy new resin.


(Edit - just re read and noticed you’re using a merlin; I’m not actually 100% on what percentage of solids they filter but it’s surely got to be better than what you’re getting?!)
To

[AuRavelling79]

That's  very poor out for a PRF. I would expect less than 10ppm on brand new membranes. Mine are six months old and producing 14ppm at the moment. In is 285ppm.
Obvs after resin it's 000.