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Buying first RO membrane - What to look for?


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I'm looking into buying a new RO membrane but all the resellers in my country charge around $700-$800 CAD. These resellers give me no information on the membrane like who makes it, what its production is rated at and for what pressure (ie 2500 gallons per day @ 100 psi).

When I look online at retailers that sell generic RO membranes like maxwaterflow.com I can't compare their products to what I have been buying although an RO membrane from them is only $220!

What should I be looking for in RO membrane for window cleaning?

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5 hours ago, KingKat said:

I'm looking into buying a new RO membrane but all the resellers in my country charge around $700-$800 CAD. These resellers give me no information on the membrane like who makes it, what its production is rated at and for what pressure (ie 2500 gallons per day @ 100 psi).

When I look online at retailers that sell generic RO membranes like maxwaterflow.com I can't compare their products to what I have been buying although an RO membrane from them is only $220!

What should I be looking for in RO membrane for window cleaning?

The cheap membranes are usually of Chinese manufacturer. They entice many by their low cost purchase price but its the usual saying; you get what you pay for.

In my opinion you need to be looking for a membrane made in the USA. They are more expensive but are usually better quality.

I can only repeat my experience;

Our tap water pressure is 50psi. The tds of our tap water is around 122ppm. I chose an Axeon HF5 membrane as I don't use a booster pump. (This membrane costs around £400 in the UK. We can purchase a cheap chinese HID membrane for less than 1/2 that - £180.00.) After 7 years my membrane is still removing 97% of the dissolved solids in our water. The output from the membrane was 3ppm this morning. My di vessel is 6 liters in size and my resin of choice is Tulsion MB115. Each refill lasts about a year.

The specs on an HF5 membrane say its OK for water pressure from 50psi to 100psi (3.4 bar to  7 bar)

The specs for the HF4 Axeon membrane 80-105psi (5.3-7 BAR). If I went to an HF4 I would need to add a booster pump.

I have 20" prefilters. The first is a 5 micron sediment filter and the second a Pentair Pentek CBF-Plus 20 Fiberdyne 5 to 10 micron carbon block.

According to the manufacturers this carbon block filter has a service life of 75700 liters. I change those prefilters on time. This is about every 4 to 5 months working on my own and weather dependent. I have a water meter on the inlet of my r/o supply so I can monitor the service time easily. So I know exactly how much water my r/o is using. 

What I don't know is exactly how much pure I use a month. But its a good guess as my pure to waste ratio is about 55% waste to 45% pure when I'm filtering water. So it looks like I'm using around 34000 liter of pure for every filter change.

There is a supplier selling even cheaper membranes but he clearly states they have a rejection rate of 80%. That's no good for a window cleaner. If I fitted that membrane my rejection rate would be around 25ppm. It would cost me a fortune in resin to polish that off (3 as to 25ppm). So the initial savings on the cost of the membrane would be negated by the extra cost of resin (about £90 for a 25 liter sack.)

 

 

Edited by spruce
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