Water hammer (new washer-dryer)

Adam Funk · 2020-03-25T12:39:55+00:00

The new washer-dryer causes fairly loud water hammer every few minuteswhen drying (I haven't any noticed noise when washing, but it probablyonly cuts on and off a couple of times over the whole programme).I've seen water hammer suppressors that fit between the appliance hose& the connector:but I don't have room for one of those under the kitchen sink,especially since I think it has to be installed pointing up.There's also the freestanding kind:which says "single-appliance", but I would have room to fit that tothe cold water supply running through the crawl space under the diningroom to the kitchen, & only one appliance is causing hammer. That onesays 1/2" BSP, so I guess the installation method is to cut a gap ofthe right size into the water pipe & fit a tee with a 1/2" BSPpointing up --- is that right?I'm also thinking of trying some more "improvised" measures first,such as wrapping the pipe in rubber (old bike inner tube) & clampingaround that to a joist --- is that realistically likely to make adifference? (The pipes below floor level are already covered withinsulation & expanding foam.)Thanks.

Mar 25, 2020 Last reply: 6 years ago 27 Replies

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NY 6 years ago

I was caught out by that. We'd just moved into a new house and the house already had a washing machine (without tumble drier). We were planning to do some building work in the room that had the washing machine, so we got the removal men to put our own washer/drier in the garage near a water supply and drain, so we could use it as a drier or as a second washing machine in the meantime.

The first time I came to use it, I plugged it into the mains but didn't connect it to the water supply because I was only going to use it as a tumble drier. And it faffed around for ages, lazily tumbling the clothes every few seconds but without ever getting to the point where blower fan started running. After about half an hour, it displayed an error code which was not one of the codes that was listed in the manual (don't you just

*love* undocumented error codes).

Then it dawned on me: being a condensing drier it probably needed a water supply even when working as a drier. As soon as I connected the hose and turned it on, the drier worked as normal.

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Adam Funk 6 years ago

I checked the hose & it's the least elastic appliance hose I've ever seen. Anyway, I looked at the in-line water hammer arrestor again & the orientation doesn't seem to matter (there's a piston in the leg) so I've ordered one to try.

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John 6 years ago

It can be any hose.

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Chris Hogg 6 years ago

AIUI the piston separates the water from the air 'cushion'. A diaphragm does much the same thing. Again AIUI, if the two aren't separated, the air in the 'cushion' slowly dissolves in the water and eventually disappears, allowing the hammer to return.

On that basis, I would think that anyone with an unvented water system and expansion vessel would be protected against hammer.

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Adam Funk 6 years ago

Just to follow up, the arrestor [1] doesn't completely silence the water hammer but does make a big difference. I'm going to try securing some of the cold water pipes too.

[1] "Sioux Chief DW660-H Water Hammer Arrestor ¾" BSP Connection" from Screwfix

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tabbypurr 6 years ago

I've found clamping pipes well to the wall with vibration absorbing lumps sometimes works. A series valve turned partly off often works. And an upright dead leg /can/ work. Any of these things can reduce the q of the resonant structure, which is what you're aiming for.

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Adam Funk 6 years ago

A section of cold water pipe in the crawl space under the dining room that had some play in it, so I strapped it up towards the joists in a few places with some "Sabrefix Builders Band Stainless Steel 20mm" (around the foam insulation that was already on the pipe). That hasn't eliminated the noise but has reduced it significantly further.

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tabbypurr 6 years ago

If the pipe is only feeding the dryer a valve would be the easiest surest plumbed fix. I always figured squeezing the pipe to reduce flow a bit should work, but never tried it.

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