Screaming cold tap

[antioch]

This is my first post. Hope I have picked the correct forum section.
Apologies if multi-posting not good practice - but posted in Valves & Taps
without any response - this forum appears to be used more frequently.
I have a Blanco sink with standard mixer taps - just over a year old.
The cold tap started dripping a week ago - replaced the washer on the cold tap and hot at the same time.
After a couple of days the cold tap would make a slight screaming noise after it was turned on - the noise was not very loud and would stop when tap opened fuller.
So changed washer again - same noise - in all I have changed the washer three times with washers from different suppliers.
I have lowered the mains flow - did not correct fault.
I swapped the cold tap with the hot tap - all OK for most of the day, then the screaming noise returned - this time with a vengence - the neighbours can hear it. This morning, the first few usages not a peep.
Then the tap would not fully turn off, and continued with a slow trickle.
And it is screaming like hell. I removed the tap, put it back - it can be turned off but the screaming is still there.
I have searched within this forum, but did not find any similar problem.
I also Googled - again no help.

I am wondering if this problem could be an inherent build fault with the internal mechanism.

I look forward to possible solutions.

Thank you
Antioch

[migoplumber]

sounds like its mains pressure related. whats your incoming mains pressure? are the taps rated for this pressure? combi boiler? tank fed?

shaun

[Dannypipe]

Yup - I'd suggest a Pressure Reducing Valve, cut into the rising main.

[bobpape]

You are experiancing a variation of a phenomena called water hammer

Allthough water hammer is effected by flow and pressure it is not caused by either,

In fact water hammer is caused by the frequency pulses inherent in pumped water acting (resonating)on the clapper in a stop/ball cock or tap

Years ago the problem was solved in most instances by teeing off into the cock (as opposed to using an elbow) and fitting a 6 or 8 inch length of capped off pipe which because of the trapped air
acted like an accumulator that damped out the pulses. I have to tell you that it does not work every time,
but in some circumstances it is worth a try,

If it is occurring in a tap try wedging the clapper spindle (a strand of wire from a wire brush works a treat) if that stops it then the tap is at fault, you either have to inhibit the propensity for the clapper to resonate, this can be achieved by raising a burr on the clapper spindle, or replace the whole tap,

If it is occuring at a ball cock then change it for a brass equilibrium ball valve or even
Torbec sometimes works,

(I have copied and pasted this reply from elsewhere on the forum)

ADDENDUM TO MY PREVIOUS POST.
I should explain.
I have not plagiarised someone elses post,

[antioch]

Many thanks to those with suggestions/replies.
Now that I have the correct terminology for this phenomenon, 'tap hammer', I am able to search further.
Why do these problems always seem to want to occur at BH weekends??? SODS LAW perhaps. In any case, with commitments today there is nothing I can do until tomorrow.

[migoplumber]

when there is less demand for a cold water supply in the street, ie certain times of day when houses are vacant, or bh weekend when people are away....
the mains pressure will be dynamically higher in your house.

shaun