Pipes banging?

[Scooterman]

I think BM was once a plumber?

When the washing machine is filling up. The solenoid valve on the cold water feed opens and closes several times while the washing machine is deciding for itself if there's enough water in the drum.

But every time the valve shuts the pipes bang. I was wondering if reducing the pressure, i.e. throttling the stopcock might help?

But some else said it might be water hammer rather than a loose pipe under floorboards? But I don't know what water hammer is?

The banging isn't that bad, and not worth ripping the floor up. But if there's an easy fix, which there probably isn't, I would do it.

[Scooterman]

EDIT: I should have added that it does also does on the rinse cycle

[Burgerman]

Yes, water hammer.
The water flows from the street, and has a lot of mass. The valve shuts fast. Instantly. The water which is a stream of water maybe a few hundred meters long hits an immovable object. That causes a shockwave to try and bounce this mass back the opposite way. It is hard to stop it doing this. If the water is slowed down via a stop tap enough to make much difference then you will be a week running a bath, etc.

You can fit a valve just on the washing machine to slow the flow here only. But there already is one. Called a washing machine tap... So use that. It wants to be shut off almost. Just cracked open so that you can hear the water slow as it fills. So it fills slowly.

[Scooterman]

That's a great answer BM I never thought about trying to throttle the washing machine tap, thanks I shall try that.

As an aside:

I worked for a water company for a while and the pumping station used to have what they called a 'surge vessel'. It was a large pressure vessel which looked like a giant propane gas cylinder. It was connected to an air compressor and kept pressurised and I think it was T'eed off the pumping main which pumped the water from the pumping station up the hill to the reservoir. All the pumping stations had diesel generator back up for when there was power cuts. But the surge vessel was there for the time lag between the power going off and the diesel generator starting up. Apparently I was told that when the power goes off, the water column that is being pumped up the hill to the res would come cascading back down the pipe and could blow apart the pipe work in the pumping station. The surge vessel apparently acted like a giant shock absorber.

NB: Down south when I started to work for them 100% of the drinking water would come from boreholes/wells. It would be pumped into a small holding tank in the pumping station, then be chlorinated in the tank before being pumped up the hill to a big covered-in reservoir, then it would gravitate downhill to houses etc. But because of population explosion they started drawing water from rivers which is a lot more expensive cos it requires a lot of filtration. Whereas groundwater from deep boreholes/wells is pure and only chlorinated as a precaution and regulations.

[Burgerman]

Well where I live we used to get water from higher ground after years soaking through layers of chalk for 30 miles in every direction. Great tasting water, pumped out of the ground and into a water tank about 100 feet high.

Until a fuel station sprung a leak, dumped thousands of gallons of fuel into the water table... And now that water has been undrinkable for a decade. There so much of it that they still have to run the pumps to prevent flooding... And pump it straight into the drains.

Now our water comes from a resorvoire...

[Scooterman]

Oh, that was a bit of bummer. I expect there was a lot of argy bargy over who paid for the clear up. We had a diesel leak when some "travellers"
cut the thick plastic sight hose that ran vertically up the side of the tank. They used it like a hosepipe to fill up their vehicles and containers then left it dangling down. And over night the whole diesel tank drained, several hundred/thousand gallons. The whole area had to be excavated and contaminated spoil got rid of, replaced and re-tarmac'd .

[Burgerman]

I think it had been happening slowly for years. The pumping station was at least a mile away from the fuel station... And clearing it up wasnt possible. You would have to dig up about 500 houses and 4 or 5 square miles...

Have a read here!
https://royaldutchshellplc.com/2008/07/ ... -clean-up/