Doubled my RO flow rate

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About a year ago I got one of these cheap 3-stage RO filters. It works well but it's a bit slow: about 5 litres/hr at 3.8 bar.

For a total of £28 I've now fitted a higher capacity membrane and matching flow restrictor, which has more than doubled my collection rate to 12 litres/hr athumb..


If you're using a booster pump then you should get even more of an increase (@Mash Monster, @Hazelwood Brewery, @hughjamton )

*** Note: if you upgrade your membrane capacity then you MUST also change the rating of the flow restrictor ***

This is my filter, supplied with a standard 50GPD membrane

Screenshot 2021-08-16 at 12.45.21.png


I used this 150GPD membrane (£22) and this 1500 ml/min flow restrictor (£6).
I'd have used a 1200 restrictor if I could have got one but the 1500 is close enough.


Screenshot 2021-08-16 at 13.14.12.png


Ignore the '800GPD' description on the flow restrict listing - the seller doesn't know what they are talking about.

Screenshot 2021-08-16 at 13.13.37.png



The new parts took less than 5 min to fit, and I've just flushed everything through and tested the new setup.

Results after 20mins

After 20 mins I had collected about 4 litres of filtered water and 19 litres of bypass water (which will be used to wash the car).

IMG_6025.jpeg
 
Last edited:
Note that the ratio of bypassed to filtered water needs to be at least 4:1 in order to preserve the life of the membrane.
This ratio is governed by the rating of the flow restrictor.

The following table shows indicative restrictor ratings for different membrane capacities. Suppliers may tweak these up or down a bit according to how sensitive they think consumers are to the level of bypass water used versus the frequency of replacing the membrane.

In hard water areas you should use a slightly higher level of bypass.

Screenshot 2021-08-16 at 14.09.32.png
 

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