[Ian Lancaster]

Does anyone know why the pure outlet elbow on a typical 100gpd membrane housing has an insert in it?  We have a problem with gradual reduction in flow of pure water from some of our RO's.

It's not a pressure issue, mains pressure is about 40-60 psi and we use Aquatec booster pumps.

On one system we tried running each membrane separately - they all have fairly new membranes fitted.  Two were producing pure, but at a very slow rate, the third was only producing a series of drips, not even enough to make a continuous stream.  We stripped down the housing and noticed that the pure outlet elbow has a plastic insert but the waste doesn't.  Why would the pure need a valve or restrictor in the outlet?

Blowing through the elbow didn't work - it was impossible to blow through in either direction.

As a last resort I'm going to try running the membrane with a clear elbow on the pure outlet but before I risk damaging a perfectly good membrane has anyone got any suggestions?

Got to admit I'm stumped on this one - it seems there's some sort of blockage that's getting progressively worse but I can't work out why.

[p1w1]

Hi Ian

There are 3 elbows on each membrane 1 of the elbows will have the insert in as this is a non return valve.  The one with the non return valve should be for the  waste (basically to stop any waste water with the high tds getting back into the purified water and protecting the membrane).
Should you need new ones they can be brought from here http://www.ebay.co.uk/itm/170648352673?_trksid=p2060353.m2749.l2649&ssPageName=STRK%3AMEBIDX%3AIT  . I have recently purchased 3 sets from them.

I personally wouldn't recommend running the waste without the valve for any long periods of time (perhaps a few days while you wait for new ones)

paul

[Ian Lancaster]

Hi Paul,

Thanks for the reply.  Just to clarify:  in the set up we have the elbow with the insert is the one on the Permeate (purified water) outlet from the housing.  If I understand you right, it seems this has been incorrectly installed by the manufacturer.  I had guessed it could be a non-return but couldn't understand why the permeate would need one.

It still doesn't explain why we have experienced this gradual decline in production, nor why we can't blow through the valve in the same direction as the flow of permeate.

The waste outlet elbow was definitely without any insert.

I will check the other two membrane housings to see if they have the elbows fitted the same as the first, or not.

Thanks for the link for replacements, I'll get some on order today.

Ian

[p1w1]

Yes the one with the valve goes on the waste water only. I'm no expert but it could be a case of a faulty fitting on your membrane or there on the wrong outlet. You could try each membrane with no valve fitted on any outlets including waste this would eliminate any other issues if all works fine. Also to bare in mind as the water gets colder flow and production to tend to get slower then in the warmer months.
i suppose another possibility is a dodgy membrane i have had this before when changing them but it wasn't a flow issue it was a tds issue.
This is why ive recently gone to a 40/40 its more straight forward to eliminate issues.

[chris turner]

Err, it's a 100gpd piece of garbage. Either use it for your exoctic fish or throw it in the bin and buy a proper RO?
With your 600 vans on the road I'm sure you can afford one

[Dave Willis]

There are some duff membranes about, friend of mine fitted brand new membranes and couldn't get any water through them, put the old ones back in and water flowed again. Dealer replaced them.

[Ian Lancaster]

Err, it's a 100gpd piece of garbage. Either use it for your exoctic fish or throw it in the bin and buy a proper RO?
With your 600 vans on the road I'm sure you can afford one

You're quite right, and I do own one 40-40.  If I did have 600 franchisees (as you mention above) and I provided them all with 40-40 RO's  it would cost me something like £400,000 and even I would struggle to manage that

[Frankybadboy]

There are some duff membranes about, friend of mine fitted brand new membranes and couldn't get any water through them, put the old ones back in and water flowed again. Dealer replaced them.

worrying thing there is you got a FRIEND

[Dave Willis]

Only the one.