[Lee GLS]

On a water meter is it better to have a lower TDS output but higher waste, or lower waste but high TDS output meaning high resin consumption. What is cheaper in the long run?

[keyser soze]

tough one . often thought about this but hoping i'll learn from  experience . sorry not been going long enough to have an idea really.

[colin purewater]

What your TDs lee ?

[colin purewater]

And water pressure to ?

[Lee GLS]

Tap tds is 375, come out of the ro at 8 with a 3:1 waste pure ratio, with nearer a 1:1 ratio, slightly more waste than pure the output is nearer 15

[Lee GLS]

I use a booster pump so it's very good

[colin purewater]

I won't class my self as an expert on the matter but I think what your getting is excellent and at that tds any other option you wouldn't gain anything mate

What you've got seem the best to me if you Tds after ro is say less than 30 your on to a winner

[Perfect Windows]

Tap tds is 375, come out of the ro at 8 with a 3:1 waste pure ratio, with nearer a 1:1 ratio, slightly more waste than pure the output is nearer 15

Looking at the maths in a back-of-an-envelope manner....

Every 1,000 litres you produce at 3:1 will use 2,000 litres more than at 1:1.  2,000 litres cost including sewerage here is £2.90, so £5.80 more per 1,000 litres.

Using the Gardiners resin calculator, that 1,000 litres of RO output running through your resin with an "excess" TDS of 7 (at £64 a sack) will cost you 82p.  Thus, for every 1,000 litres pure at 3:1, you're looking at paying a net £4.98 more.

You also need to factor in the membrane life, but I'm testing that out at the mo.  My RO output has gone from 10 to 12/13TDS over two months of producing 1,000 litres a working day (input ~280).  That's roughly 40 working days, so I've already saved about £200 in water charges; much cheaper to have a slightly shorter life from the membrane.  That doesn't take into account a slowly rising cost of resin in the future; I need to do some more work to calculate the break even point on that one, membrane vs resin.

Lots of holes available for picking in that maths, but should be in the right area.

Hope that helps.

Vin

[Lee GLS]

thanks for that vin. How long and how often do you flush your RO on a water meter?

I'm not on a meter at the moment, but should be moving and will be on one so I want to work everything out before hand.

[Perfect Windows]

I flush it every day - it takes ten minutes for the van to fill; the RO is flushed for that long.

Vin