Membranes in series…flow meters?

[Tweegs]

I’m building an RO this summer. While I’ve found the answers to many of my questions here, one remains.

If two XLE 4040’s were connected in series, how would the permeate flow meter be connected?

Would you monitor the permeate outflow from the first membrane only, the second membrane only, or would you combine the permeate outflow of both membranes before sending it past the flow meter?

If I were to wing it, I’d say monitor the second membrane only, but I’d like to confirm.

[BreezyHill]

Our unit is setup one pair in series and the flow meter is the combined flow. While it would be nice to know the output of the two individually I can not. I will be adding another pair parallel to the first pair since the xle require so much less flow than my system was built for.

This is a low pressure flow so plastic tubing will be fine, and tee the outputs together and thru the flow meter to the storage tank.

[sapman28]

Mine is also in series and the flow is combined.

[Tweegs]

Thanks guys,
Easy enough to do.

[Russell Lampron]

The permeate and concentrate flow meters are mounted on the control panel of my RO and both measure the output of the machine. The RO's from the maple manufacturers are made this way. If you wanted to measure the output of each membrane separately you would have to put flow meters after each membrane.

[mellondome]

You could put a flow meter on each towers output. Then you dont have to bring the permeate back to the panel.