[mac74]

Hello all, 
Anybody have any info on a twin 40" RO setup. The reason i ask is because i use 2 x 20" pre filters, into a single 40" RO unit, then into a 7L ressin vessel. My TDS is 410ppm -  I always boost the water pressure with a draper 1000w pump from 35psi to 70psi (70psi  is the sweet spot) and it makes 200L per hr. (100L per hour unboosted) When i put a new RO in, the TDS comes out about 12ppm - then afer 2 years it goes to about 25ppm - then year 3 it goes to about 35ppm. This is seems ok, but im wondering if doing a twin RO setup will give me, the under 10ppm needed to go straight onto the glass, without needing the use of resin? and how long it would take to make water boosted/unboosted? When the RO is new, i reckon i do a sack per year (12ppm) - and now (25ppm) maybe 2 sacks a year it seems? and when it reaches 35ppm it will probably be 3 sacks a year. A sack of Unger resin is now £94ish, so i wanted some advice on weighing up the costs? and trade offs of the above Q's. Many Thanks m

[Spruce]

As the material the membrane is made from ages the minute holes in the fabric get bigger through wear and tear and any chlorine getting through the prefilters.

The tds of your pure increases because more particles can pass through those bigger holes.

Your water is pretty hard so this would also add the a reduction in service life of the membrane.

According to one of the suppliers, your membranes are due for replacement when the tds of your pure reaches 25ppm (94%).  If the tds rose to 35 in the next year, the cost of 2 extra sacks of resin would go a long way towards paying for a new membrane.

What membranes are you using?

I don't believe that using 2 x 4040 with help your water purity much - it will give you a little more pure per minute provided your water supply could keep up with production.
 

[mac74]

Thanks for the reply spruce, i use a axeon hf4 - so at 25ppm, you think i should change it then? is there any way of cleaning it, maybe to get another year out of it?  Cheers m

[Richard Groves]

Thanks for the reply spruce, i use a axeon hf4 - so at 25ppm, you think i should change it then? is there any way of cleaning it, maybe to get another year out of it?  Cheers m

http://www.cleanitup.co.uk/smf/index.php?topic=216312.0
I'm about to try this as someone has given me their old membrane that was at 25 ppm also ( which is'nt far off what my 4040 membrane is producing now )
I've built a container to house it from a 1 meter length of soil pipe and blank end caps.

[dd]

If you fit a water softener this should increase the membrane life.

I have a static set up in the garage with a softener fitted.