RO Membrane still usefull ?

It seems like I have excessive waste water. 1 gallon of waste water only produces 3 1/8 cups of RO/DI at 0 tds. My input is at 425 TDS, RO is coming out at 15 TDS. I use a pump to get input pressure up to 70 PSI. Filters are 6 months old and the input comes out of a water softner.

 

How old is the membrane ? How old is the filter and carbon ?

 

1 Gallon of waste water should produce 0.25 gal of pure water (usual 4:1 ratio). You're at 0.2 (approx.) So that's not bad really. What is your water temp going into the filter? This could account for the discrepancy. I'm sure AZ will chime in soon, he's the go to with RO in my books lol.

 

You're thinking is right on the money here. The ratio reported by the OP isn't that far off from the 4:1 and water temp is the likely cause.

If you want to change this ratio, crank your pump up to 80 psi. or spend $4 on a different flow restrictor.

Russ

 

+1 to azdesertrat! Btw, you should probably be changing your prefilters, sediment and carbon filters, every 6 months (unless you are using a pressure gauge to measure their functionality). This will protect your RO membrane and extend its life. You cannot test this with a TDS meter as the prefilters do not remove TDS, I believe they remove suspended solids.

 

You are very close to 4:1 waste ratio (128 oz/25oz) or about 5:1 so thats not your problem.

I would increase the pressure to 80 psi or higher personally, I run my system at 90-100 psi which increases the GPD and the rejection rate both which still being well within the pressure rating of the membrane and housings. In winter months the ratio may change due to colder water but it can be overcome with higher pressure and i would not suggest trying to warm the water.