RODI - How to adjust waste water ratio?

[GarrettT]

I’m confused on how to adjust my spectrapure 90gpd RODI.

Product water - 300
Waste water - 950

I would like to get the waste water to 1200. I have the red flow restrictor, but it came precut to about 1/2”.

Would putting a ball valve on the product line to reduce some of the product water work?

 

[KStatefan]

You can purchase a long restrictor then cut it to the length you need. That ratio will change with changes in your pressure or temperature.

 

[GarrettT]

That’s what I figured. I’ll go ahead and place the order. Thanks.

 

[gabrieltackitt]

The flow restriction on RO membrane is based off of what is ideal for the membrane itself. I wouldn’t put any kind of flow restrictor on the product line. You could change the restrictor on the waste line though.

why are you wanting to change this, though? The waste restrictor is an integral part of keeping your membrane efficient and healthy, not sure you should be changing it just because you want a different amount of wastewater output.

 

[GarrettT]

why are you wanting to change this, though? The waste restrictor is an integral part of keeping your membrane efficient and healthy, not sure you should be changing it just because you want a different amount of wastewater output.

Most people recommend having a 4:1 waste water to product ratio.

 

[KStatefan]

That’s what I figured. I’ll go ahead and place the order. Thanks.

Do you have high tds or hard source water?

 

[gabrieltackitt]

Most people recommend having a 4:1 waste water to product ratio.

Have you checked the recommended ratio for your particular membrane?

on my 75gpd my ratio is around 2.5:1 and about 3 tds after the membrane.

just because that’s what people recommend doesn’t necessarily mean it’s a requirement.

 

[DrZoidburg]

Custom flush with needle valve. Tightening needle valve gives more water but more tds to resin. Also higher psi.

 

[GarrettT]

Do you have high tds or hard source water?

Average tds and very hard water source.

 

[gabrieltackitt]

Average tds and very hard water source.

With higher levels of hardness you may benefit from a higher product to waste ratio, but you should contact spectrapure support to see what they recommend. They would probably be able to tell you exactly what part number flow restrictor you need.