Advice needed re recharging a water hammer arrestor

[Biilee]

Hi, I would be grateful for advice regarding how I can recharge a water hammer arrestor.

Background:

Just over 2 and a half years ago the old gravity system in my medium sized 3 bed semi was converted to a pressure combi-boiler system by British Gas. Immediately after this I experienced water hammer in my pipes (something I had not experienced before). I complained to British Gas and they installed a water hammer arrestor, which significantly reduced the problem. However, the arrestor now seems to be failing as I am again hearing a heavy clunking sound in the pipes whenever the toilet cistern is filled after flushing and whenever I turn off my taps after running water from them.

The arrestor is located on the cold water feed that leads to the combi-boiler (a Baxi). The boiler is situated on the first floor landing in my 'airing cupboard', which used to house the old gravity system's hot water cylinder. The arrestor is positioned about 18 inches below the boiler.

The airing cupboard is right next to the bathroom and it also houses the electrics and plumbing for an instant shower over the bath.

The arrestor was installed by British Gas to stop all of the taps in the house - both hot and cold - from clunking, i.e. kitchen sink, bath and wash hand basin taps.

The arrestor also reduced somewhat (but not totally) the clunking heard when my washing machine stops filling and when the toilet cystern stops filling.

The arrestor also stops cold water from shooting out of the instant shower above my bath. (I'm not sure, but if my memory serves me correctly, this used to happen either when the taps in the kitchen were turned on and/or when the toilet cystern was filling - It's not happening at the moment, but I think it's only a matter of time before it happens again.)

A picture of the arrestor can be seen by clicking on the following link or putting it into your browser if that doesn't work (sorry, I tried to upload an image, but it was not successful)

[DLMURL]http://tinyurl.com/mky564g[/DLMURL]

British Gas didn't leave any manufacturer's instructions/details about the arrestor and I don't know its make. It looks similar to others that I've seen on the Internet, which are pre-set to 3.0-3.5 bar with a capacity of 0.16 litres. (Its size is just a bit larger than a tennis ball.)

Questions:

How do I do the recharging? What process do I go through?

Do I just simply turn the water off at the stopcock and run all of the cold water taps to empty the system first and then add (pump) air into the arrestor?

I've read elsewhere on the Internet that the arrestor could be recharged with a mountain bike shock pump, which I understand would have the advantage of not letting any air escape during the removal of the pump after recharging; would it do the job?

If after recharging the arrestor should fail again, would it be best to get it replaced with a mechanical arrestor? Would a mechanical one do the same job, and what type and make would be advisable?

If I were to get the arrestor replaced with another chamber arrestor, am I likely to get longer service life with a more expensive one? (They seem to range from about £20 to £40.)

Many thanks if you can help.

 

[Cello]

I have a similar device on my thermal storage system although I guess that its job is to accommodate expansion in the (essentially closed) system. I recharge it every 12 months. I turn off the water supply valve and depressurise the water side by turning a tap on. I then check the pressure in the device (it usually has not gone down much) and then repressurise to 5 bar using a tyre inflator. The main problem is that due to the very small capacity of he device you have to be quick with the disconnection to avoid significant loss of air.

 

[Biilee]

Thanks for your reply, Cello.

The main problem is that due to the very small capacity of he device you have to be quick with the disconnection to avoid significant loss of air.

I was reading elsewhere on the net that a mountain bike shock pump works in such a way as to prevent such significant loss of air - but obviously I haven't as yet tried this myself.

Can you or anyone else advise what procedure I should follow to recharge an arrestor on an open system, i.e. a system that feeds the cold taps, an instant shower, a toilet cystern and also provides the feed to obtain hot water from the combi boiler. The arrestor is, I believe, located on the cold feed pipe that divides into two branches, with one side going to the combi boiler and the other side going to the instant shower (a photo of which is in the link in my first posting on this thread).

Many thanks.

 

[Ermintrude]

You will need a pump with a pressure gauge.

Locate data badge on the vessel. Find out it's change pressure.

Turn off cold. Open all taps. Attach pump and pressurise to req pressure. Turn off taps and turn on cold. Job done

Taps will sputter and spit. Tun shower onto cold and run for 1 min to purge all the air. .

If you can't pressurise the arrester means it's ka poop

 

[Biilee]

Thanks Ermintrude.

Unfortunately, there's no data badge on the vessel/arrestor. I've had a look at similar arrestors on the net and the majority are pre-set to 3.5 bar with a minority pre-set to 3.0 bar (all with a capacity of 0.16 litres, which I think is almost certainly the size of the arrestor concerned). Am I liable to damage the arrestor if I recharge to 3.5 bar?

Also, just to check - when you say turn on all the taps, does that include all of the hot taps as well as the cold taps?

If the arrestor can't be charged and it's therefore ka poop, would I be best to replace it with a mechanical arrestor instead of a rechargeable chamber arrestor? If so, is there a make and type that you could recommend?

If it's best to just replace it with another chamber arrestor, am I likely to get a longer life from a more expensive one, do you think? (My current one will have only lasted just over two and a half years and my guess is that British Gas will have fitted the cheapest arrestor possible.)

Many thanks again.

 

[Ermintrude]

Charge to 3.5 bar. If replacing use non mechanical it's a lot more durable. U could fit a domestic hot water expansion vessel .

 

[Ermintrude]

Oh and just cold taps

 

[Biilee]

Thanks, Ermintrude - that's really helpful.

If I were to replace the chamber arrestor/vessel with another chamber arrestor/vessel is it a case of the more expensive the better or are they all much of a muchness?

 

[Ermintrude]

Volume is the thing normally

 

[IDCHAPPY]

Have you tried changing the fill valve on the toilet?

 

[Biilee]

Thanks Ermintude - So, is it a case of the bigger the vessel, the better the result? (Although the current vessel/arrestor - when it was working properly - stopped the water from shooting out of the shower and greatly reduced the water hammer when turning taps on and off, there was still a little bit of a clunk when the washing machine fill turned off and after the toilet cystern filled and closed...so would a bigger vessel would have an even better result?)

 

[Biilee]

Thanks IDCHAPPY - No, I haven't tried changing the fill valve on the toilet as the water hammer occurs not just in relation to flushing the toilet, but also when closing both hot and cold taps. So I thought that this problem might be down to the arrestor failing/needing to be recharged. Could I be wrong about this? Could a malfunction of the fill valve on the toilet also cause water hammer when the hot and cold taps are closed?

 

[Biilee]

A big thank you to Ermintrude! I followed the instructions given to the letter (and used a mountain bike shock pump - purchased from Halfords for about 20 quid - which worked as hoped and didn't let any air out of the arrestor upon releasing the pump).

Am very pleased and grateful for the advice 🙂

 

[Biilee]

An update: In the end the water hammer arrestor didn't hold the recharge, so it had partially failed at first and then ended up failing altogether and needed replacing. The replacement has solved the water hammer problem just as its predecessor had done so I didn't need to change the refill valve on the toilet, although when the refill valve needs replacing I will opt for a 'quiet fill' one.

Thanks to everyone who replied to advise me - I greatly appreciate it.