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Noisy RO Filters

Guest bazniff

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Guest bazniff

I have a Pure Freedom 250 gpd RO system. Ive had it for 2 and half  years, problem free. Regular flushing and replacement of pre filters. 

Now heres the issue. I have recently moved house and since I moved and set up my gear in my new garage the RO filters make a groaning noise. This noise then transmits back down 10m of hose to the outside tap which sits under the kitchen window and is supplied from the cold water feed just under the sink.


This groan, by the time it reaches the kitchen is really loud, infact it is unbearable if you are in the kitchen or the bedroom above. 


To solve the problem I have done the following:


1 Replaced the outside tap (no difference)

2 Tried longer / different hose ( noise got worse)

3 Replaced all the pre filters and resin ( made no difference)

4 Run the outside tap on its own unconected to anything ( runs silently, no noise in the kitchen )

5 Removed the shut off valve ( made no difference)

6 Flushed the RO filters a few times and agitated / moved the RO filters to get rid of any air bubbles. ( There was air bubble inside, but getting rid of them had made no difference).


Has anyone encounteted this before, or anything similar?


My other half has threatened that if I cant cure it ill have to go back to ladders and a rag and I really dont want to do that unless I have to.


Any help or suggestions appreciated. 


Many Thanks



Edited by bazniff
Mis spell
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When I fitted a manual shut off valve we experienced water hammer when the unit tried to shut off. There were no instructions with this valve but I later discovered that I hadn't connected it up correctly. (I never went back to it as I fitted an electrical solenoid valve when I bought an IBC tank.)


You need to try to identify where the noise is coming from.


If you partially close the tap that feeds your r/o, do you get the same noise.


Is the stop valve under the kitchen sink fully open? Is the noise emanating from this valve?


If you disconnect to pipe that feeds into the r/o housing from the prefilters and turn the water on, do you still have the same 'groan'.


Then you may need to look at your waste restrictor. If its just an open and close tap, can you remove it and try to find some other way of throttling back the waste to see if the noise is still there?


Do you have a float valve in your storage tank?


On a slight twist of this, we used to get water hammer in our pipes. It wasn't continuous and we could never understand where it was coming from or what caused it.  Switching off the tap under the sink didn't stop it either. Running the hot water proved it wasn't the ball valve in our header tank. (I replaced that just in case.) We flushed the toilet but that didn't stop the noise either.


Then the old lady next door to us went into hospital and the problem never occurred when the house was unoccupied. Her boiler packed up whilst she was in hospital and her 'carers' arranged for a new boiler to be installed. I spoke to the British Gas engineer went he was fitting the boiler and he told me that the noise couldn't possibly be coming from her house. Anyway, she came out of hospital a month later and we never had an issue after that. (BG removed her header tank and water storage hot water tank and replaced that with a combi boiler.) She died a few months later and the house was sold.

The only thing we get now is a hammer (one 'knock') when next doors washing machine switches off on its washing cycle. We live in a semi detached house and these are our 'attached' neighbours.


Our water supply is separate. We are the end house on the water main and theirs is the second end house. We each have our own outside stop valves in the pavement.



Edited by spruce
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Guest bazniff

Hi Spruce, thanks for the reply


I have partially opened and fully opened all the various valve and taps in line. Still no change, the groan / scream is still there.


The groan is continuous as long as the RO is filtering. Not just when something is being turned on or off.


My tank doesnt have a float valve.


Its definatly me and not my neighbours thats making the noise ( heehee)


The thing I havent done is disconnect the RO filters from the waste yet. I will try that later this morning.


I did give the RO filters a shake and a light whack last night to disodge any air that might be inside. There WAS quite a bit of air that I heard being shifed when I did. I now doubt there is any air in the system now to cause any noise issues. 


One of the things I was wondering is could my RO filters be worn / blocked / faulty and somehow causing back pressure or water hammer.


This little Gremlin is proving to be a real head scratcher thus far, but later this morning I will see if its hiding in the waste tap etc.


I suppose if the worst come to it I can just buy a new RO system ( yikes ).







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Guest bazniff

I have managed to work out this morning that when I put my RO filters in flush mode the groaning noise reduces to almost nothing. Its cirtainly bearable. 


However once I turn the flush tap back to normal working position the groaning noise comes back as bad as ever. 


Anyone got any ideas. Im stumped. 

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Guest bazniff

Ok Spruce


I have already changed all the prefilters. 


I do agree with you that appears to be the flush valve. I will look at it more tomorrow and talk to Pure Freedom on monday. 👍

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