Finally got round to working out how to backflush the merlin today. The unit is just over 2 years old, produced a tds of 30 when new ( my supply is very high though, about 350 - 400) It had risen to 42, have just changed pre filter and backflushed for 20 mins with pure from vans tank through di, read the waste a few times until it was down to 000. Re-assembled it all and initially it was producing 32 but has now risen back to 42. Have I backflushed long enough? if not how long? or is it more likely, as I suspect, that the membranes are gradually deteriorating ?
Thanks
Simon