Thump noise when turning off taps sharpish

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Hi, any suggestions appreciated
After a leak in the supply pipe to my property (15mm copper/blue plastic coated) 1974 bungalow, I have a replacement water feed of the modern blue pipe which I think is 25mm. The only other thing that has changed is I have had the meter under the sink relocated to the boundary box in the pavement, the pipe from boundary to house is approx 9mtr in length, is goes back to 15mm plastic and through insubox entering wall to under sink. Last night I noticed a thump sound in pipes when sharply turning off either the hot or cold taps. It is only when you close the taps, is this what I'm assuming is called water hammer? Tonight I was gonna check the pipes for any contact points in the loft over bathroom as we were turning the water off in the street for a while when not in use because of the leak and running pipes clear of air each day for a while, is the thump due to the increased size of the pipe? Would an easy solution be to choke it back a bit at the pavement at the stop valve? We have always had ample pressure for the last 20yrs. TIA Neil
Update:just been tracking the noise and found it was loudest going back to the boiler, when you close the gate valve on the cold water boiler feed it goes away, when you open it...the noise comes back in that pipe, regardless of how much it is open, very bizarre.
 
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With the increase in pipe size you will now have maximised pressure and flow to the property. Now any 1/4 turn taps and solenoid valve closing can create water hammer (shockwaves travelling along the pipework) and where pipes are not clipped properly and are loose can tend to knock/bang.

Shock arresters only treat the symptoms, they don't fix the cause and should only need to be used where there is unusually high water pressure.
 
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Think I'm gonna see if things settle down and maybe add an arrester later if nothing changes, as I had a 120ltr per hour leak for a while and there was a bigger leak around the corner and today I've noticed another fresh dig up, I'm just wondering if the waterboard may have increased the pressure temporarily, we'll see
 
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Is that a combi boiler? The valve you mention being the supply for hot water? If yes then start looking for loose hot water pipes- remember when that valve is open you have a direct hydraulic connection from cold to hot.
 
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Is that a combi boiler? The valve you mention being the supply for hot water? If yes then start looking for loose hot water pipes- remember when that valve is open you have a direct hydraulic connection from cold to hot.
The valve was the cold supply shut off to the boiler, I've bought a diaphragm type arrestor that I'm gonna locate on the cold pipe under the boiler as a trial, going to utilise the old obsolete fill loop point from the cold feed(cap off, connect the diaphragm with a flexi to the 1/2 bsp and open valve) and see if it does the job, I'm confident it will make the difference
 

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