Mains supply Whenever i turn off pretty much any cold tap in my house suddenly i hear what sounds like water pipes under the house banging/knocking.If I turn the tap off slowly it dosnt seem to happen
have tried turning on every tap/hose etc on the property and leaving it to run in case it was air lock but didnt make a difference
In theory you need a chamber with air in it, somewhere in the system. I've never seen one installed. My water pressure was so high I put a pressure reducing valve in, and it fixed all my plumbing problems.
csador,
Jan 22, 7:24pm
hmm I might try turning the pressure down at the mains.I'm pretty sure this only started when i had to turn the mains off to fix something else, so maybe I have it up too high
cantabman1,
Jan 22, 9:47pm
Yep, an air lock in the system is causing your problem.
40wav,
Jan 22, 9:56pm
No it isnt.
40wav,
Jan 22, 9:57pm
Do you have a pressure reducing valve on the line in! Or just the isolating valve.
carter19,
Jan 23, 12:43am
How old is the house! How long has the problem been there!
siobhan41,
Jan 23, 1:07am
We have the same problem in our 1950s house with copper pipes and were told its nothing to worry about. But saying that it was a builder not a plumber telling me that.
davea74,
Jan 23, 1:23am
We had the same thing, it was a bit of pipe under the house that had come loose, and the 'water hammer' when the tap was turned off was making it bang against the beams.
debbie214,
Jan 23, 2:00am
I had that and it used to drive me crazy. Plumber couldn't fix it. He secured some pipes with no effect. I happened to get a new shower installed and it stopped immediately following that. Not sure what the plumber did but so glad it stopped!
trade4us2,
Jan 23, 3:07am
Turning the mains tap almost off could stop the water hammer. However if you want a good volume of water, e.g. for fighting a fire, that's not the best solution. All it needs is a device almost anywhere in your system that has an air chamber. I believe that device will have to be emptied of water occasionally. If I had an outside tap that's not being used I would attach the air chamber to that. However my pressure reduction valve has fixed all the plumbing problems in my house that were caused by an incredibly high water pressure from Metrowater.
gypsyguy,
Jan 23, 1:02pm
Sounds like water hammer to me. You can buy a thing called a water hammer arrestor which can be instlled out of sight somewhere in your plumbing, that basically acts like a shock absorber for your water pressure. Worked for us.
antoniab,
Jan 23, 1:19pm
Our taps in the kitchen do that - man if you turn it on in the middle of the night to get a drink its sooo loud! Old rental house so doesnt really worry me.
caspar26,
Jan 23, 2:41pm
The water hammer arrestor that everyone is talking about can be installed inline on your dishwasher supply or washing machine cold supply. it definatly is water hammer but it also sounds like the pipes under your house needs some extra clipping or strapping up. also check if you have a pressure limiting valve, because that may have failed. By turning the water down at the mains tap will only decrease flow, not pressure so that will definatly not solve your problem. The water hammer is caused by the water coming out at a high velocity and stopping very fast, ie on a washing machine soleniod valve or mixer tap. Hope this helps. Bevan
spirogryo,
Jan 23, 6:47pm
Nothing to worry about! Yes it is.Get it sorted before it wrecks your plumbing.
csador,
Jan 23, 7:52pm
thanks for the replies, i might just get a plumber in to take a look as I dont really want to muck around with the plumbing too much myself
do get it sorted asap it is water hammer and doesn't necessarily mean air in the pipes
a wee story, a lot of farmers now fit water rams wherever they can get approx 5 mts of drop with reasonable flow
a water ram is made with 10mm steel construction, sometimes even thicker for larger models, and if you set it into operation and do not open the valves it will quickly build up enough pressure to burst either the galvanised pipe exit or the cylinder ( twice the size and thickness of a gas bottle), most will pump water 130mts uphill minimum, they cost maintenance only to run and run for many years with no maintenance at all I've been guilty of it once, the sight and sound of 700 psi whizzing past your head is not a good memory, it blew a hole the size of a basketball in a filled concrete block wall approx 1 mt away, probably missed me by about a mt but I sure would notwant it to be any closer
40wav,
Jan 24, 12:16am
What does this have to do with water hammer in domestic plumbing!
skin1235,
Jan 24, 8:08pm
what pressure do you imagine ( or know) is required to push water to a 130 mts head
without an accumulator there is very little volume but the pressure is still there mains pressure running through a full open tap then suddenly shut off develops that same pressure, its the shock wave from that sudden pressure build that you call water hammer
domestic water systems are not made of strong enough materials to withstand those shock waves - water rams built of 10mm steel cannot even withstand then for long
but while you query the info you give an excuse for lack of resolve, and that can be a delay that eventuates in burst fittings inside walls etc
murphy's law says the pipes will burst at 10pm on a friday night in the middle of a 5 day storm, probably the same weekend that every plumber in the area is away camping and won't be back til tuesday ( any time plumbers go camping is sure to a stormy week anyway)
skin1235,
Jan 24, 8:12pm
suggest until it is sorted you change the way you turn the taps off, do not just slam them closed, close them slowly, gently, - take it as a challenge to not have the pipes hammer - it can be done
if your plumber turns up and says there is no issue, or is an issue and he can fix it by whatever, then fine, my advice was perhaps a little heavy ignoring the issue because you think my advice may be a bit heavy without getting it checked could be a folly
elect70,
Jan 24, 10:21pm
Buy doz1/2 ' copper pipe saddlesget under the house & saddlepipes to everyfloor joist they cross.
40wav,
Jan 25, 12:44am
You mention 700 psi, this equates to 4800 kpa. No domestic plumbing is going to create (or withstand) that kind of pressure. This is my point. The water hammer created in domestic plumbing running at, say, 700 kpa from a town supply, MIGHT create 1000 kpa max with water hammer. It will do this anyway whether the pipes are secure or not. It's when the pipes are not secure that the noise happens. The options are- 1. If the plumbing is accesable i.e. under the floor, secure the pipes better OR 2. if the pipes are not accesable i.e. in the walls, install a $150 PRV on the inlet line and reduce pressure to an acceptable level that eliminates the hammer OR 3. install a hammer arrester as mentioned above (I have no experience with these and would not use one as my prefered method would be pressure reduction).
40wav,
Feb 7, 11:14am
130 mts head (or 1300 kpa) is not the same as 700 psi.
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