[WGB]

As above. I have a RO 40/40 and TDS reading is sitting about 023 just after membrane at, should i replace soon??

[Spruce]

As above. I have a RO 40/40 and TDS reading is sitting about 023 just after membrane at, should i replace soon??

You need to give us some more info. Tap tds? Membrane's age. How many liters a week you process, etc

For example, if your tap water tds was 750ppm, then 23 pure is still within the membrane' s spec. 

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[Smudger]

Isn't tds that high illegal

But yes the example given is correct

Darran

[james stanley]

23 is fine m8 .... Look to change above 35 ...

[SeanK]

My 4040 membrane is working out at around £40 a year (6 years use ) so for me I change it when its costing me
more than £40 extra  a year in resin.
Go by costs not ppm count.

[Arnold Palmer]

95% efficiency.