Hi..there doesn't seem to be a search engine so rather than read the 350 pages here in "techies corner" may I ask for advice directly. I'm trying to alleviate the knocking sound when the taps turn on. I understand I can install water hammer arrestors and believe they out to be on each pipe so I'll need 6 in total. AA (mini) arrestors for 3 utilities. Kitchen sink, most importantly. Bathroom sink and shower.
I've found them at Bunnings for about $70 each but AliExpress have the same stainless steel AA arrestors for about $7 ea. I understand the Aust stand water pipes are 12mm so I'm thinking to buy 6 arrestors from AliExpress and I'll need 6 "T' connectors to place them inline the pipes. I like the look of the "quick connectors but am unsure as to whether the AA mini arrestor just screws into the 'T", (also avail AliExpress) Any advice greatly appreciated!
Hi Peter,
My understanding with pipe hammer is when you turn taps off fast (ie with the modern lift up-push down taps). Is your question relating to a house or a van, motorhome? I haven't experienced it with our van yet but since having a new kitchen installed in our house, it does occur when my other half cannot remember to turn the tap off carefully.
I installed an anti-hammer device where the cold water feed came into the house - it certainly reduced the hammer effect on all outlets but when the plumber replaced our HWS, he removed it. I certainly need to get it reinstalled again.
There is a "Search" on this forum but it is limited & for some reason it has lost some of its effectiveness.
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Warren
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If you don't get it done today, there's always tomorrow!
Are we talking about a house? Water hammer is a funny thing. I started with a pressure reducer at my water meter as we had a water pressure reading of 700kpa. Houses should be around 500kpa so I'm told. A mate up the road got a new hot water unit installed and in a very short time it blew up, apparently from over pressure. A lot of new appliances don't like over pressure now. It wasn't covered under warranty because of the pressure. He had a reducer installed at the meter. Don't know why this wasn't done with the new installation. After our pressure reducer was installed we didn't like the pressure the water ran at and it didn'tfix the problem. Walking the dog up the road and my mates neighbour was having getting a reducer installed, I stopped and had a chat to him and as he was installing a variable pressure reducer told him to stop off down the road and I'll have one. So reducer mk2 went in, but pressure setting was not changed. Didn't fix the hammer either. So off to my hot water system. There is a flow valve (I'll call it that) on the hot water system. After a few years this can cause water hammer to be produced. Got that changed and the water hammer was gone. It does also depend on how fast you turn the taps on or off. It didn't matter if cold or hot tap was used. Also we got water hammer with the dishwasher and washing machine. All that was fixed after replacing this flow valve thing.
Oh, in the end I didn't change the pressure setting, we just got used to it.
-- Edited by Corndoggy on Saturday 14th of February 2026 08:43:15 PM
Water hammer can commonly be due to an airlock whether it be in a van or a house. Open all taps starting from the lowest and furthest, also flush the toilet or toilets a number of times. Let it run for a couple of minutes and then from the furthest taps work backwards turning them off.
If you are talking about your home, a simple solution for water hammer may be to partially close the main tap at the entrance to your property. That's what our plumber did for us and it has worked well.
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I think it was Dorian a few weeks ago mentioned use the "" with the search engine and it works a treat.
I had severe water hammer at home for a few weeks, it was driving me crazy, so I did the turn the water off at the mains and close them off in the recommended order.
That didn't work.
So I changed the washers in what were the two highest water taps that seemed to be the main offenders and it worked a treat.
The old washers were a bit worn in parts and must have been allowing air to get into the system or the water running backwards or something to that effect.
Dunno - but the effort by changing the washers seemed to work in this instance.
