[Steve foster]

Hi, could do with some advice please on my TDS readings. Along with others mine is starting to play up and its looking like the membrane is on its way out.
Last week I was getting 00.6 going into the tank, this week its 015. The system has always given low readings and I do not use resin.
Input pressure around 65 psi with 136 tds. After playing around with the waste to find the lowest tds sweet spot. Around 50-55 psi gives best reading.
Changed filters today and de-slimmed the RO vessel and frequently back flush the system.
Managed to get 010 at the mo and thats it. Also tried a booster pump but made no difference.
My membrane is coming up for its 11th birthday  so reckon Iv'e had my moneys worth out of it.
Can you guys recommend 1 for me please?   
Thanks Steve.

[PoleKing]

TDS out at 10...
Get DI, it'll last for 200,000 litres at that
£200 odd for the big vessel and resin-cheaper than replacing the RO

[Spruce]

Hi, could do with some advice please on my TDS readings. Along with others mine is starting to play up and its looking like the membrane is on its way out.
Last week I was getting 00.6 going into the tank, this week its 015. The system has always given low readings and I do not use resin.
Input pressure around 65 psi with 136 tds. After playing around with the waste to find the lowest tds sweet spot. Around 50-55 psi gives best reading.
Changed filters today and de-slimmed the RO vessel and frequently back flush the system.
Managed to get 010 at the mo and thats it. Also tried a booster pump but made no difference.
My membrane is coming up for its 11th birthday  so reckon Iv'e had my moneys worth out of it.
Can you guys recommend 1 for me please?   
Thanks Steve.

It's time to replace the membrane. At that age is bound to become less and less efficient and will have to be replaced anyway.

We have a tap pressure of between 40 and 50 psi. We have an umpumped system with an HF5 membrane. I was told by Purefreedom that the HF4 would work just as well with that pressure, but went with my gut instincts.

I would probably give June a ring at GAPS and ask her opinion on which membrane she would recommend. I think that the HF5 would still be good at that pressure, but I would seek professional advice on this one if I were you.

Due to these membranes initial cost, buying the wrong one would be a waste of money IMHO. Please let us know what she recommends. Thanks.

[Steve foster]

The Di setup seems ok, but due to age of membrane its due for renewal anyway.
Was toying with the HF4 membrane as the water pressure is easier to regulate and wont have to worry about lower pressure in winter.
I will give June a ring at Gaps.
Thanks.

[Steve foster]

Having taken the advice about talking to June at Gaps, the recommended membrane for me is the HF4. This is apparently what is in the system as the HF5 is fairly new. Both work the same only the 5 gives a quicker fill with less waste and the 4 gives a lower TDS which is what I need as not using resin. The 4 is more suited to my 70 psi tap pressure also.
Plenty of good advice given. It would seem that flushing more than 15min is a waste of time as your only removing surface partials anyway. A twin RO system will not lower TDS only the waste water, and a membrane will not work on a TDS of lower than 40.
All sorts of good advice.
Many thanks for the heads up.

[Spruce]

Having taken the advice about talking to June at Gaps, the recommended membrane for me is the HF4. This is apparently what is in the system as the HF5 is fairly new. Both work the same only the 5 gives a quicker fill with less waste and the 4 gives a lower TDS which is what I need as not using resin. The 4 is more suited to my 70 psi tap pressure also.
Plenty of good advice given. It would seem that flushing more than 15min is a waste of time as your only removing surface partials anyway. A twin RO system will not lower TDS only the waste water, and a membrane will not work on a TDS of lower than 40.
All sorts of good advice.
Many thanks for the heads up.

Cheers. I'm confused as to why the membrane won't work on a lower tds than 40 though. Did June not mean an HF4 not working on a psi lower than 40?

[Steve foster]

It seems that a membrane needs a min of 40 tds to work. She was saying they had problems with Scottish customers having less than 40 tds from fhe tap. She mentioned an electric charge that is present in higher Quantities of tds and thats how the membrane works. I know its the electric resistance that it measured from the tds meter. After that i'm lost.
This was because I mentioned fitting a second membrane unit but only having about 15 tds going in to from the first membrane. But it does not work that way. Both units act as 1 and give the same tds but even lower waste water.

[Steve foster]

New HF4 membrane fitted and its back to 001 at 50-55 psi. And 002 at 60 psi. Yabba Dabba Doo time . And only cost £216 
 Still managed to clean on about 012 with no problems, just giving a good rinse.