Water Hammer from Toilet

I have read many posts about this problem and the answer is usually "replace your ball valve washer". I have had a look in my toilet and I do not exactly which part is the ball valve, although I do know which part of the mechanism causes the water hammer. Also the parts that causes the water hammer are made from plastic and do not have an existing washer in the assembly.
I get water hammer through my pipes just as the cistern is at the end of its refill. The long arm attached to the float has what looks like a plastic screw mounted on it at the opposite end to the float. As the float rises this screw pushes a "piston" into a "cylinder" (a valve??) which eventually stops water flowing into the tank. If I flush my toilet and push the piston with light pressure I can reproduce the water hammer effect. The fact that the flowrate into the tank slows as the piston is pushed in makes the water hammer noise last longer.
The piston and cylinder (valve?) are made from a white plastic. The piston fits loosely but I cannot pull it out of the cylinder. Does the washer go into the cylinder before the piston, preventing the piston from vibrating as it is slowly closed? B&Q have a ball valve diaphragm washer for 98pence(http://www.diy.com/bq/category/category.jhtml?CATID 735. Is this what I need?
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On 2 Dec 2003 07:59:48 -0800, snipped-for-privacy@hotmail.com (anon) wrote:

You have identified the ball valve correctly.
Replacing the washer may help but generally the problem is due to pressure/flow being too high.. You could try that first, and then if not, fit some form of flow restrictor like a service valve in the pipe. A more drastic solution is to replace the ball valve with a Fluidmaster or Torbeck type. These come with a flow restrictor which fits in the valve itself.
.andy
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(anon) wrote:

A torbeck valve has the added advantage that it operates over a very small change in level - maintaining full flow until *just* before it shuts off. This would be a direct replacement for your existing ball valve, and very easy to fit - but the bit inside the cistern is much smaller than a conventional ball valve.
Roger
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The trouble with a Fluidmaster is that it cuts off the water very suddenly. This could make water hammer even worse. Isn't one cause of water hammer due to un-clipped pipes?
I fitted a Fluidmaster with some difficulty. It is a bottom fill cistern and the valve needed to be at the same end as the handle / siphon which limited space. I also had difficulty adjusting the height of the water without the valve body preventing the lid from fitting properly.
--


Regards

John

> > >I have read many posts about this problem and the answer is usually
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snipped-for-privacy@hotmail.com (anon) wrote

I'm no toilet expert, but I believe water hammer occurs when the flow is abrupty stopped. e.g. when turning off a tap sharply, causing standing waves back down the pipe.
Is the ball valve sticking, do the mechanisms move smoothly ?
Alternatively, new inlet valve assembly's are cheap enough, i'd change it as in some cases it'd be easier than trying to diagnose what's wrong inside your current one.
HTH
Cheers.
Paul.
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snipped-for-privacy@technologist.com (Zymurgy) wrote in message (anon) wrote

Thanks for all the replies. Everything moves smoothly until the water level is nearly full and the ball valve starts to close. The piston part vibrates inside the cylinder part which is what causes the water hammer. This loud humming noise goes on for about 20 seconds until the valve finally closes. I expect that the vibrations of the valve cause the flow to be started and stopped repeatedly at high frequency, causing the hum.
There doesn't appear to be a washer inside the assembly, so maybe the valve has become loose allowing it to vibrate. If I push the valve with my finger, partially closing it I can cause the humming noise.
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(anon) wrote

<<snipped>>
Have a look on the pipe feeding the cistern to see if there is a service valve. It looks very like a straight plumbing connection, but it has a small slot on a circular shaped piece in the middle.
This service valve will allow you turn down the water flow which reaches the cistern, and will also reduce some of the pressure being placed on the float valve inside.
Flush the loo and then put a screwdriver in the slot on the service valve. When the hammering begins, turn the screwdriver slowly until it stops. Flush the loo again and make sure the water is still flowing fast enough to fill the cistern quickly, but not under to much pressure that it causes the hammering.
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(anon) wrote

the
float
SORRY !!! I mean till the hammering stops, not the screwdriver.

to
the
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