I bought a Power Devil model PDG4024 in 2001 from the local market for £20. It has given years of good service but about 2 years ago it lost pressure. I filled it with 5% white vinegar and forgot about it for a couple of weeks. 6 months or so ago my son told me it was playing up again. This time I stripped it down and gave it a good cleaning with acetic acid, have put it back together and unfortunately the bypass valve is passing when it should not be. I am going to try and acid clean it and exercise the valve in situ or take it out (assuming it will come out, it may be stuck through scale in the water) and replace the O ring.

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