Phil
heres apost from another site, you can work out exactly how much water 25l of resin will purify, and subsequently the cost at approx £65.00 per bag
An 8" diameter column 35" high holds about 22 litres of resin. We use virgin Dow MB50 resin, and 22 litres of this resin will mop up 500,000 units of impurities. So you divide 500,000 by the TDS of the water you're putting in, the result being the litres of water you'll get out before the resin has to be changed. For example, if the TDS of the water from your RO is 5ppm, an 8x 35 column will produce 500,000/5 = 100,000 litres. If you're one of the lucky ones, and your mains water is only 50ppm TDS, the same column could produce 10,000 litres, at a cost in replacement resin of only £70, and you may not need to invest in an RO. Hope this helps!
thanks
Julian
