RO Membrane Calculater

[macca]

Hi. How is this done plz. I have tap water going in at 324ppm through a 450gpd RO and before the DI it's 24ppm and then through a 7 Lt vessel coming out a 0ppm but doesn't really last for long, say a couple of days before it goes up to 2 ppm. Do I need a bigger vessel? Thanks

 

[Dave B]

Wcw and gardiners have a resin calculator

450 in should be about 14 ish out so that is quite high anyway

My water goes through di at 11 and 7l vessel lasts ages

 

[spruce]

Hi. How is this done plz. I have tap water going in at 324ppm through a 450gpd RO and before the DI it's 24ppm and then through a 7 Lt vessel coming out a 0ppm but doesn't really last for long, say a couple of days before it goes up to 2 ppm. Do I need a bigger vessel? Thanks

You need to get the the root cause of your membranes inefficient removing of dissolved solids to reduce resin useage.

Your membranes are working at 92.6%. So they are removing 92.6% of the dissolved solids/salts in your water. An efficient membrane will be removing 97 to 98% of the dissolved solids. I was once told that the time to consider membrane replacement is around 94% rejection rate.

(324 - 24 = 300. Divide 300 by 324 = 0.9259. Multiply by 100 = 92.59%)

How old are your membranes?

It could be low water pressure. It also could be 'worn out' (age related) membranes or membranes destroyed by chlorine due to extended prefilter changes. It also could be a rouge membrane that is infecting the pure from the other 2 membranes.

Running the r/o and testing the pure from each membrane will identify a rouge. If they are all the same and you have good water pressure, then you will need to replace membranes and prefilters. Then stick to the replacement schedule recommended by the prefilter manufacturers.

 

[macca]

Thnx Spruce. The membranes are old so as you suggest replacement is key and the Pre filters also. Cheers mate.