Tds reading

Evening my tds reading is 60 before it goes in the RO and my water reading goes from 000 to 006 after 100 Ltrs any ideas I've changed resin and pre filter kit

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tommy15468 said:

Evening my tds reading is 60 before it goes in the RO and my water reading goes from 000 to 006 after 100 Ltrs any ideas I've changed resin and pre filter kit

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What the tds of the pure coming from you r/o?

What di vessel are you using?

Change resin and it's 000 for about 100ltres then slowly over next hour or so goes up n up n up


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tommy15468 said:

Change resin and it's 000 for about 100ltres then slowly over next hour or so goes up n up n up


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I'm looking for the tds of the pure from the membrane/s before it goes to the di Vessel.

That's 60


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tommy15468 said:

That's 60


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Right. So what you are saying is that your water into the r/o from the tap is 60ppm. It then goes into the prefilters and then after the prefilters it goes into the r/o. When you measure the pure water leaving the r/o its 60ppm, the same as the tap water tds.

It then goes into the di vessel at 60ppm. It comes out of the di vessel at 000 after you change resin but creeps up quickly.

What should happen is that your water comes into the r/o at 60 and passes through the prefilters where any sediment and chlorine are removed. It should then enter the inlet of the membrane housing where 97 to 99% of those total dissolved solids are removed. At 60ppm the water exiting the r/o should read about 1ppm. It will enter into the di vessel at 1 and the resin in the di vessel will polish it off to 000.

At 1ppm the resin in one of those small 10" di vessels supplied with some r/o's should last a while as its doing no work. But at 60ppm it stands no chance.

So to me it sounds as though your membranes are goosed. But I've never heard of a membrane no working at all.

If cared for a membrane should last for quite some time. I got 6 years from my 150gpd membranes on my 450gpd r/o. I bought it second hand and it was one year old. The membranes had to be replaced as the previous owner didn't replace the prefilters.

The first prefilter is a sediment filter which traps and particles larger than 5 micron. The second prefilter is a carbon block and removes chlorine. Chlorine destroys membranes. Some carbon block (C/B) filters only have a service life of 10000 liters which is waste and pure added together.

If you run your r/o at a pure to waste ratio of 1 to 1 then this c/b filter will work for 5 x 1000l IBC tanks of pure. If your ratio is set the 3 waste to 1 pure then you will only get 2.5 x 1000 ibc tanks of pure before it needs replacing.

So regular prefilter changes are a must.

Some don't realise that there must be water going to the drain (waste) whilst they are producing pure. If they shut the waste valve off entirely then they will destroy their membrane.

How do we decide when to replace membranes?

A membrane won't remove 100% of the impurities in the water, but we need it to remove as much as possible. The more efficiently the membrane works the less resin we use polishing those remnants of dissolved solids off.

We should be quite happy with our r/o removing 97 to 98% of the dissolved solids in our tap water.  If the tap water tds was 100 then that should leave a tds of 2 or 3 after r/o. Once the membranes start to reach 94% efficiency the tds output reaches 6 and that's generally the time to consider replacing membranes.

.

Sorry out the tap it's 265


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Spruce and Doug are the are full of great info and I defo not got the knowledge these guys have but 260 tap then 60 from RO sounds to me that your membranes are shot, my tds is between 280and 300 and 009 after RO 

tommy15468 said:

Sorry out the tap it's 265


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So your membranes are only working at an efficiency of 77%. (265 - 60 / 265 x 100 = 77.4%).

Membranes need replacing. If they have failed prematurely then you need to identify the reason why.