[[GQC] Tim]

What should be the percentage Pure to Waste roughly on a 4040? A search on the forum showed some varying figures. I assume 50 to 60% waste is good for optimal life expectancy?

TDS in 280ppm
50psi pressure

[Pj]

There's 2 ways of looking at this:

1.  Go by supplier/manufacturer recommendations for preserving the long life of your membrane.  Which will probably be something like the ratio you're thinking.

2.  Put an inline TDS meter after your membrane, if you haven't done so, then ease your waste to optimal production.
 Depends whether you're bothered more about volume of waste or life of membrane.  There may be a bit of trade off.

[[GQC] Tim]

Yea I would like to preserve the membrane a bit.

I read on RO man it should be around 3 to 4 gallons per gallon of pure, that seems very excessive doesn't it? That's like 75% waste.

I'm not on a water meter though, so I'm not too bothered about waste, but still wouldn't like to waste that much.

[Pj]

Well, you've answered it yourself really.  Follow their guidelines.

I go at about 50/50  and sometimes 60/40  (40% waste).
Maybe that's why my membrane only lasts 3 years max!

And I'm on a meter

It all gets recycled...eventually.

[[GQC] Tim]

3 years is not too bad I would say. Is that with a softener as well?

Think 50/50 sounds about right. I think it would help tremendously if we had some database with all the figures in it. A simple forum search turns up too many things.