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We have an unvented hot water system which was working fine until just over a year ago in our 8 year old house.
The boiler comes on once a day to heat the hot water in the early morning and we noticed that the first time we turn the water on after this, we get a loud and distinctive noise from the airing cupboard. The noise actually sounds like someone hitting the pipework hard and quickly repeatedly and usually goes on for about a second, but has been known to go on for 5 or 6 seconds occasionally (I have videos of this if it helps). This only happens the first time the hot water is turned on after the boiler has run. We notice that, in combination with the noise the hot water pressure drops from an initial high, down to a slightly lower pressure, which is then the pressure we receive at all other times.
The local plumber came out and suspected the non-return valve on the cold mains feed and so replaced it, which did not make a difference. On following visits, on the instructions of the cylinder manufacturers, he changed the pipework to the expansion vessel from a flexible hose to copper pipe and then moved the T connection closer to the pressure reducing valve. Finally he tried replacing the expansion vessel (a total of about 5 visits). All of these changed the character of the noise in various ways (it would be longer, shorter, make a noise when turning off the water as well as on) but never solved the problem.
Just recently, we also occasionally hear a much quieter version of the noise when the boiler first turns on to heat the hot water - not sure how long after the boiler turns on because I'm usually half-asleep.
There are some related facts as well. About 8 months before we first had this problem, we had a water softener fitted. This has reduced the cold water pressure slightly, but I have tried taking the softener out of circuit and it doesn't help with the noise. We have also noticed our mains water pressure into the house has reduced considerably. We used to get around 2.2-2.5 bar and now we get about 1.3-1.4 bar. I've checked with neighbours and they are getting the same pressure we are.
Has anyone experienced anything like this or got any theories as what it could be? Is it likely to be related to the reduced water pressure, and if so, is there anything we can do about it?
The boiler comes on once a day to heat the hot water in the early morning and we noticed that the first time we turn the water on after this, we get a loud and distinctive noise from the airing cupboard. The noise actually sounds like someone hitting the pipework hard and quickly repeatedly and usually goes on for about a second, but has been known to go on for 5 or 6 seconds occasionally (I have videos of this if it helps). This only happens the first time the hot water is turned on after the boiler has run. We notice that, in combination with the noise the hot water pressure drops from an initial high, down to a slightly lower pressure, which is then the pressure we receive at all other times.
The local plumber came out and suspected the non-return valve on the cold mains feed and so replaced it, which did not make a difference. On following visits, on the instructions of the cylinder manufacturers, he changed the pipework to the expansion vessel from a flexible hose to copper pipe and then moved the T connection closer to the pressure reducing valve. Finally he tried replacing the expansion vessel (a total of about 5 visits). All of these changed the character of the noise in various ways (it would be longer, shorter, make a noise when turning off the water as well as on) but never solved the problem.
Just recently, we also occasionally hear a much quieter version of the noise when the boiler first turns on to heat the hot water - not sure how long after the boiler turns on because I'm usually half-asleep.
There are some related facts as well. About 8 months before we first had this problem, we had a water softener fitted. This has reduced the cold water pressure slightly, but I have tried taking the softener out of circuit and it doesn't help with the noise. We have also noticed our mains water pressure into the house has reduced considerably. We used to get around 2.2-2.5 bar and now we get about 1.3-1.4 bar. I've checked with neighbours and they are getting the same pressure we are.
Has anyone experienced anything like this or got any theories as what it could be? Is it likely to be related to the reduced water pressure, and if so, is there anything we can do about it?
