water hammer

Had water hammer in previous property I owned 30 years ago, cured it by bending the ball cock arm a little to the side................but I'm not a plumber!

 

Hi SC.

If you have a gravity system, then most of your taps are fed by the low pressure from your storage tank, and that is very unlikely to cause water-hammer.

So the likely culprit is the kitchen cold.

The causes of 'hammer are numerous - simple loose pipe lengths, loose washer in the main stopcock wot vibrates, worn/loose washers in any ballcock such as your CWS (cold tank), toilet cistern etc.

Basically wot happens is that the abrupt change in pressure inside the cold mains pipe when a tap is turned onski or offski creates a pulsing wave which can sometimes keep itself going; you open a tap, the pressure falls, the washer moves...you turn the tap off, the pressure rises again, the washer is slapped back on to its seating. This makes the pressure drop fractionally - enough to make it slightly open again. Pressure now rises suddenly - and you have a bad case of the MCs.

(If you turn the cold tap off slowly, does that prevent it?)

Sooooo, you need to find oot where the 'source' of t'ammer is.

(How helpful was that?)

 

So I'm wrong on every single count?

Wait a minute!

Ooops - no. Every single count...


Can you confirm - this new gas system, it ain't a combi boiler, is it? Or do you still have your gravity-fed hot cylinder with immersion?


Anyways, I suspect you are right - a floppy washer in the hot tap. Ceramic disc type should sort this.

 

Oookkkaaayyy - either you need to improve your grammar, or I need to not jump to conclusions.

I think a bit of both...

I'd read, from your first post, that you still had a gravity system, and just had a new boiler fitted - not a change of system to combi.

In which case your 'hots' are also mains fed so that makes sense in it capable of causing 'ammer.

Good chance it's as you say - your old hot tap has a wobbly washer inside, and it's shaking around shutting t'flow onski and offski as it flaps around.

Very good chance that a new, ceramic disc, tap will sort it.

If it doesn't, then perhaps your mains water pressure is nicely high so could benefit from having a PRV installed. Or, you can fit wee vessels that are designed to absorb all these shocks and stop 'ammer. I've also read that water meters can cause this to previously ok systems, and that the WB should fit shock arrestors as standard - or is it that they should be fitted to all combi systems anyways? I dunno...

So, good idea to replace the tap first.

 

I had the same problem and it turned out to be the mains cold water stop valve to the house. It was not opened fully, as soons as the plumber opened it fully all the hammering stoped. Worth a try.

 

I wouldn't go further than this one - good brand, good reviews, good price: http://www.screwfix.com/p/swirl-rapture-dual-lever-deck-mixer-kitchen-tap-chrome/53252

The actual tap fittings should be the same, but I wouldn't be surprised if they were at slightly different heights. So if you want to chop the two pipes and add flexis to make life easier, then flexis with built-in isolating valves would make sense. Eg: http://www.screwfix.com/p/flexible-tap-connector-with-valve-15mm-x-x-300mm/3558g

You can start the job by chopping both pipes (er, water shut off first, of course...) and shoving these on. Once fitted, you can then turn the water back on and do the tap replacement at your leisure. All your cold taps will now have fresh mains water.

Just make sure you cut the pipes at the right point...

(One review says the valves drip. In this case chust leave the tap connector ends sitting in a pan...)

 

As a first step, fit a full bore maintap. Sometimes a length of plastic pipe can solve the problem as well. Try the obvious first. The full bore maintap will give a higher "flow" into the house.

 

Don't solder within 250mm of it, don't kink it and make sure you use the correct inserts, i.e. use hep inserts with hep pipe, not speed fit for example. You can join straight onto it with a compression or push fit fitting. Congrats on sorting the water hammer. Lastly I'm not being pedantic buts its 22mm not 3/4inch.

 

Yep if your just replacing like for like your spot, on, undo the old one, stick a bit of boss white or jet blue round the olive and do the nut back up to the new tap. The plastic normally has a fifty year guarantee, Hep2o does for example. It won't get brittle. Only thing to check is that the previous plumber used inserts. Good luck!

 

It should hopefully be just as easy as the sink taps. In fact, it should be more easy as the plastic pipe allows more movement.

If it's a normal tap connector, there should be a fibre washer in there (like on the sink ones), so check it's good, wrap PTFE around it, or use a smear of compound.

Should be fine.