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I have an inline tds meter with 2 sensors on my 4040. The first sensor is on the pure output after r/o and before di. The second is just after di. In our case we store pure water at 000 (that's the idea anyway.)

What you need to find out is why the water is now leaving your di vessel at 1.

Your tds output from r/o seems to be right as the r/o membrane is running at about 98% efficiency. Now you need to confirm that this is the case and take samples and check it with your hand held tds meter. If these figures are right then I would be focusing on the di vessel.. Purefreedom supply a 6/7 liter di vessel as standard and that resin should purify about 70,000 liters of pure at 9ppm according to Gardiner's resin calculator.

Does giving the di vessel a shake improve the tds?

How much resin is there in the di vessel?

Has the di vessel failed in some way? The di vessel has a riser tube inside. If that isn't seated in the housing or if something has happened to the o ring that seals onto the riser tube, then you could get water just bypassing the resin in the vessel.

If you shake the di vessel around then remove the header, the water inside the di vessel should be pure. If it isn't, then the resin is at fault.

When filling your di vessel up with new resin, always put some water into the di vessel after you have put the resin in. It makes it much easier to push the riser tube back inside.

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Ok spruce I understand all that, what about quality of water will a twin di clean the water as good as an r/o as r/o have different filter and membrane etc to clean the water where as di is just resin ?
At the end of the day water at 000 ppm is pure. It doesn't matter if it was done with resin only or r/o and resin.

The quality is the same in window cleaning terms. Purifying water is cheaper per liter with an r/o than with resin only if you are in a hard water area.

Its also exactly the same resin you are using to remove the final 2% of impurities in the water, so its doing the exact same job. From a water sample you won't be able to tell which has been done with r/o and di or just di on its own.

(We aren't talking about the system Ionic sells that purifies water from ppm to ppb. That needs a special resin.)

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Thanks Spruce

I have a inline tds before and after d.i so my thinking was it's the d.i.

But wasn't sure why it was 0 one day and 1 next.

A freind said something similar the d.i vessel was pre filled by them so chance's are it's not full.

I will give it a shake and check how full etc tomorrow.

At first I thought the flushing could effect it as pure freedom say to disconnect the input hose to d.i when flushing but what your saying makes sense.

 
Thanks SpruceI have a inline tds before and after d.i so my thinking was it's the d.i.

But wasn't sure why it was 0 one day and 1 next.

A freind said something similar the d.i vessel was pre filled by them so chance's are it's not full.

I will give it a shake and check how full etc tomorrow.

At first I thought the flushing could effect it as pure freedom say to disconnect the input hose to d.i when flushing but what your saying makes sense.

I have exactly the same size di vessel PF sell with their system. My water exits my r/o at 2ppm. My resin lasts about a year before it creeps up to 1 permanently. I shake the vessel a couple of times and It gives me an extra few days. I am fully aware of tds creep but I have never bothered about it.

We have a float switch in the tank. Take water out and the r/o kicks on and replaces it automatically. Our water is relatively soft at 99 - 125ppm. I flush probably once a month for 5 minutes.

In 2015 we used approx 13500 liters of pure a month, a little less last year as we lost a cleaner.

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