Half diagnosed problem, how to fix and what info to give a pro Plumber

[motomob]

Like many people I have one of the dreaded pulsing showers once it is switched off. I read many posts here and elsewhere on the internet and came to the conclusion mine could be due to incorrect installation and or air trapped in the system.

So diagnosing, my shower is a mixer with a thermostat dial and single operation button. Pump is recessed & hidden behind a tiled wall in the shower so I have no idea what it is or how it is plumbed.
Fed by 1.5 year old combi boiler in the roof. One bathroom house, no other showers, no water tank.

Normal operation, set to middle temp, press button wait 20-40s depending on heating status and shower is at set temp. Time to achieve desired temp has no effect on pulsing. Flow of water does vary ever so slightly during this period but not vastly. Something others reported I saw in threads that during this period steam from the hot water feed can cause air pockets.
Switch off shower, immediate pulsing on the shower itself in the hose and on water pipes hidden under the floor and behind the walls. Now getting so bad I'm worried the pulsing is impacting their mountings. Pulsing can last up to 5 mins.

With my new found dangerous internet knowledge, I tried diagnosing. In the bathroom is a toilet and sink with separate hot and water taps. Before switching the shower on I opened the cold water tap to half flow. Switched on the shower and ran it for 1-2 minutes. Switched off and lo and behold no pulsing. Turned off cold water tap.

Tried test again but this time using the shower for 5-7 mins. Switched on cold water tap at quarter flow. Used shower for 5-7 mins, when shower stopped mild less pulsing than before was present. Whilst it was pulsing I opened the hot sink tap as well to half flow and the pulsing immediately stopped.

So my ask to the forum, is there enough information above to give the exact problem to a good local reputable plumber to work off? If so what kind of fix would he need to do based on this information. If there is a known fix for this behaviour, how much roughly am I looking to fix it. I'm not looking to do this myself just want to avoid multiple visits and hopefully fix in one go.

Thanks in advance for reading and any help.

 

[steadyon]

1. If you have a combi boiler, normally you shouldn't have a pump on the shower, as to do so would mean that you are pumping the mains, which you aren't allowed to do.
2. The exception is where the combi is used to heat a VENTED hot water cylinder (vent pipe from top of cylinder terminating in an inverted "J" over the cold water storage cistern), when you might well require a pump to increase the pressure of hot water from the cylinder.
3. If the combi is used to heat water in an UNVENTED hot water cylinder (with internal or external (white or blue) pressure vessel), again you should not have a pump.
4. It would help if you could let us know what boiler you have, whether or not you have a hot water cylinder and if you do, whether it is vented or unvented.

 

[SimonG]

To be honest it's a waste of time. Nice detailed description but I would want to have eyes on. You might in fact struggle to find somebody to help. You would be better phoning somebody and just giving a brief "I'm having water hammer after using my shower, its mixer shower running off of a combi boiler".
But that's just me, hope you get it sorted

 

[motomob]

1. If you have a combi boiler, normally you shouldn't have a pump on the shower, as to do so would mean that you are pumping the mains, which you aren't allowed to do.
2. The exception is where the combi is used to heat a VENTED hot water cylinder (vent pipe from top of cylinder terminating in an inverted "J" over the cold water storage cistern), when you might well require a pump to increase the pressure of hot water from the cylinder.
3. If the combi is used to heat water in an UNVENTED hot water cylinder (with internal or external (white or blue) pressure vessel), again you should not have a pump.
4. It would help if you could let us know what boiler you have, whether or not you have a hot water cylinder and if you do, whether it is vented or unvented.

Thanks for the reply, boiler is a Worcester Greenstar 30i. Shower mixer is a Aqualisa.
There is no hot water cylinder I can see or find. It may be the shower is not pumped, I just presumed it was as the pressure is pretty decent both on the shower an on every tap in the house. It is a small house.
How could I diagnose if the shower does have a pump without removing the tiles?
Photos of the setup incl boiler attached.

 

[motomob]

To be honest it's a waste of time. Nice detailed description but I would want to have eyes on. You might in fact struggle to find somebody to help. You would be better phoning somebody and just giving a brief "I'm having water hammer after using my shower, its mixer shower running off of a combi boiler".
But that's just me, hope you get it sorted

Appreciate the reply as well, I understand the eyes on approach I was just hoping to make it as easy a call as possible for someone so as they can come and fix the problem in one job and me obv save money in not having a diagnosis visit and then the remedial.

 

[SimonG]

That looks like a digital shower. Shouldn't have a pump if its fed from a combi. You need to find the processor for the shower.

 

[ShaunCorbs]

Did you have a cylinder before?

 

[motomob]

That looks like a digital shower. Shouldn't have a pump if its fed from a combi. You need to find the processor for the shower.

The shower itself is only 2 years old but everything wears out I guess. It's making more sense that there is no pump as the boiler is at the top if the house and everything is fed underneath it.
Not looking cheap, tiles off and processor check and or replacement then by a bathroom installer and plumber then. Might be cheaper to swallow the water cost of having the sink taps on during every shower. Maybe not.

 

[motomob]

Did you have a cylinder before?

No cylinder has ever been present as far as I can see tracing the pipes and the house doesn't have space for one.
The shower was re-tiled 2 years ago and the mixer replaced then. It then slowly developed the problem afterwards.

 

[ShaunCorbs]

So in theory it should be the high pressure one

I believe the manufacturers do a repair service maybe

 

[Ben-gee]

That processor box says A1, this is the high pressure one with no pump.

If the shower is playing up the first thing to try is a reboot. Turn off the processor for 1/2 an hour then turn it on and it will reboot .
See what happens.

 

[motomob]

So in theory it should be the high pressure one

I believe the manufacturers do a repair service maybe

Thanks, as SimonG mentioned before, eyes on with these things is needed as I didn't even realise that was the shower processor. Currently unplugged for the 30mins Ben-gee has recommended.

 

[Roy_66]

Hi Moto, you have some great answers to try. For hiring the pro which seems sensible here with complex products, as Simon says, keep your initial request to just describing the problem, otherwise it may just confuse.

I'd keep using the workaround until you get a fix. My only thought is if it does turn out horrifically expensive, is there space to add a small accumulator in one of the feeds (not sure of regs there). Does sound like though shower is faulty do best fixed if poss.

Best of luck.

Cheers,

Roy (amateur at everything)

 

[motomob]

That processor box says A1, this is the high pressure one with no pump.

If the shower is playing up the first thing to try is a reboot. Turn off the processor for 1/2 an hour then turn it on and it will reboot .
See what happens.

Unplugged the processor for 30 mins. When plugged back in it made a servo type noise for 2-3s.

Ran shower for 3 minutes, first 0-40s the temperature light flashed as it mixed the dialled in temp. Then turned solid for 10s.
It then started flashing again for 10-15s as it mixed again and then turned and stayed solid.
Normal behaviour for the past year. Ran shower for 3 minutes and turned off and massive hammering as we've had for 6 months now. You can hear the pipes behind the walls hammering the wall as I fear the mounting has been damaged.

Whilst the hammering was going I turned the cold water tap on the bathroom sink to full and it ever so slightly reduced the hammering. Turned the cold tap off as not really helping.

Turned the hot tap on the sink onto full and within 1-2s the hammering was completely gone.

So now I'm unsure is,
1) the processor faulty or
2) is as I read on here and elsewhere on the internet, this down to a hot water feed that is too hot from the boiler that produces steam as it mixes in the first minutes and so in turn an air pocket in the hot water pipe.

This to me might explain how when I open the hot water sink tap it releases that air pocket and the hammering goes? Could a solution be to turn the boiler temp down from it's current 50 as per the earlier photos?

 

[Roy_66]

Unplugged the processor for 30 mins. When plugged back in it made a servo type noise for 2-3s.

Ran shower for 3 minutes, first 0-40s the temperature light flashed as it mixed the dialled in temp. Then turned solid for 10s.
It then started flashing again for 10-15s as it mixed again and then turned and stayed solid.
Normal behaviour for the past year. Ran shower for 3 minutes and turned off and massive hammering as we've had for 6 months now. You can hear the pipes behind the walls hammering the wall as I fear the mounting has been damaged.

Whilst the hammering was going I turned the cold water tap on the bathroom sink to full and it ever so slightly reduced the hammering. Turned the cold tap off as not really helping.

Turned the hot tap on the sink onto full and within 1-2s the hammering was completely gone.

So now I'm unsure is,
1) the processor faulty or
2) is as I read on here and elsewhere on the internet, this down to a hot water feed that is too hot from the boiler that produces steam as it mixes in the first minutes and so in turn an air pocket in the hot water pipe.

This to me might explain how when I open the hot water sink tap it releases that air pocket and the hammering goes? Could a solution be to turn the boiler temp down from it's current 50 as per the earlier photos?

Good experiment to turn down the boiler thermo, say 40percent?

(Thanks for conf hot tap more effective workaround. Leave shower running, sneak out, turn on hot tap . . .)

Roy