Installing a shock arrestor

[InThrees]

Hi folks

We've an issue following some recent plumbing work (involving two separate plumbers, so no responsibility taken by either!).

Essentially, our boiler now kicks in for 10-20 seconds whenever the cold water shuts off (e.g. turning off cold water tap, every time the washing machine draws cold water, etc). After some research I've gathered it is most likely caused by air in the system and I'm to ensure all pipes, dog legs, etc are bled of air. I've done so (from what I can tell - my house is very old) with no effect. Plumber surprised it has happened as didn't think there was much going on with stray pipes, etc.

Anyhow, I think my fix will therefore have to be installation of a shock arrestor. I think I can fit myself but I have a couple of questions. The picture below shows a tiny dog leg, bottom left (excuse the knackered paintwork!). My plumber over the phone suggested that a suitable location to install.

I'm to shut off the water, relieve the pressure by activating a tap and fit an arrestor. This one looks suitable - https://www.screwfix.com/p/pegler-peg62-water-hammer-arrestor-male-threaded-connection/1044V.

So, does this sound correct or all wrong?!

Thanks all.

 

[gas112]

location fine use this one though

Error 410 | Screwfix

Thousands of products at low trade prices | FREE next day delivery available | 30 day money back guarantee on all orders.

www.screwfix.com

And this fitting

Flomasta Brass Compression Adapting Female Coupler 15mm x 1/2" - Screwfix

Order online at Screwfix.com. Female couplers. FREE next day delivery available, free collection in 1 minute.

www.screwfix.com

or this one if no room

Flomasta Compression Adapting 90° Female Elbow 15mm x 1/2

Order online at Screwfix.com. Female elbows. FREE next day delivery available, free collection in 5 minutes.

www.screwfix.com

 

[InThrees]

Thanks very much for the swift response. And the process of installation, have I got that right?

 

[gas112]

Thanks very much for the swift response. And the process of installation, have I got that right?

yep water off , open tap upstairs and down let it drain out you will get some come out when you take cap off so have a bowl ready

 

[InThrees]

Out of interest - is the shock arrestor you recommended more suitable or just a better product than the Pegler version?

 

[gas112]

it is more suitable and the type fitted on 99% of combi boiler installations

 

[InThrees]

Aaaand my last question, is thread sealant necessary for this fitting?

 

[gas112]

PTFE Tape 12m x 12mm

Order online at Screwfix.com. Suitable for use with water only. FREE next day delivery available, free collection in 5 minutes.

www.screwfix.com

 

[Madrab]

You may find it's not air rather a pressure pulse heading back down the cold pipework when the other outlets are closed, when that pulse heads back along the pipework and up into the boiler, it tricks the flow sensor in the boiler into thinking there's HW demand and fires up the fan. Would it be correct that the tee at the bottom right of that pic is the cold feed heading out to the other outlets and the same pipe with the tee where you will be putting the arrestor?

If so an alternative to the shock arrestor could be a check valve on that cold pipe after the tee and that should stop the pulse heading back to the boiler.

What work did the plumbers do? It's usually caused by the solenoids on appliances or 1/4 turn ceramic valves as both close quickly, that stops the water flow suddenly and that sends a shock pulse back down the pipework (sometimes results in water hammer).

 

[InThrees]

Would it be correct that the tee at the bottom right of that pic is the cold feed heading out to the other outlets and the same pipe with the tee where you will be putting the arrestor?

Yes, I think so, although my plumbing knowledge is pretty much zero.

What work did the plumbers do?

I’ve had a kitchen sink and tap moved 4 feet along the kitchen, a dishwasher fitted, and final fit on an en suite bathroom with shower upstairs.

 

[InThrees]

By way of an update, perhaps for anyone searching the internet for solutions. In a small window of time I attempted to fit the part. On realising the olive was going to need more effort to remove than I’d hoped, I refit the cap and turned the water back on and planned to attempt another time.

I then quickly discovered the issue was fixed! In other words, I recommend anyone with the same issue firstly shut off their water, drain the system by turning on their taps and then turn the water back on. Plumbers and many others might have tried this first, but I did not! ‍

 

[Loofah]

I'm glad I came across this thread as it's highlighted I have a water hammer issue that I should get sorted I now have to try and figure out which pipe does what in the spaghetti of pipework...