Advice - Shower shutting off and pulsing Combi / Mixer

[Andymoz]

Guys, I’m turning myself inside out here – Please help!

There are many similar discussions posted, but none with my exact symptoms.

Original shower / boiler combo working fine for 10 years, however recently when taking a shower, the water will shut off with a thud and pulse with significantly reduced flow. Issue occurs at random intervals during every shower. The problem is managed by slowly regulating the supply valve to approx 50%, if opened further or operated rapidly, flow drops and pulses.

Specs:
Boiler – Baxi Combi 105e
Shower – Originally Triton Alcor / Replaced recently with Triton Themes
Pipework - Copper 15mm / braded flexibles up to the shower body

Checks complete:
Annual boiler service IAW manual (burner and heat exchanger removed / injector clean / filters etc)
Replaced incoming scale inhibitor
Checked CW inlet / DHW / Flow regulator filters (all clear)
Water company have confirmed pressure / flow correct at the tap
New mixer shower fitted, thinking the issue could have been due to a faulty thermostatic valve.
New shower gives the same issue.
New shower body filters proven clear
New shower body existing check valves replaced with combined check valve / flow limiters, IAW manual
New shower head / hose fitted, issue present whether shower head if fitted or removed

Observations:
Central heating functioning correctly
Boiler clear of warnings / faults
Shower isolating valves are open fully
Braded flexible hoses have no twists
All other taps around the house work fine (even with maximum pressure drop and all taps operating at once)
All other taps provide hot water, even when operating rapidly
Boiler getting old, but other than this shower issue it functions correctly

I’ve now reached a dead end, and thinking of checking the flow regulator / flow priority assembly / flow priority micro switch? But before go changing more components, your thoughts are welcome?

This problem is driving me mad, all advice is appreciated

Andy

 

[king of pipes]

Can you watch the boiler when the shower is running see if the boiler is switching on off on off ? take the showerhead off check for restrictions I am thinking the boiler tempreture is building up in the boiler when you regulate the shower and switching it off you need a certain flow rate through the plate heat reduce it to much and it will go off ? Just a couple of things to check there . Kop

 

[Andymoz]

Can you watch the boiler when the shower is running see if the boiler is switching on off on off ? take the showerhead off check for restrictions I am thinking the boiler tempreture is building up in the boiler when you regulate the shower and switching it off you need a certain flow rate through the plate heat reduce it to much and it will go off ? Just a couple of things to check there . Kop

KOP - When the boiler is running normally it does not cycle. Shower head is new and symptoms are the same with head removed and water allowed to free-flow. When the shower is working the flow is good, then shuts off all of a sudden, almost like a slam. This is what I'm scratching my head over, if there was a blockage, it would always be bad? Many thanks Andy

 

[king of pipes]

Does it slam then go cold it could be a faulty cartridge in the shower I have searched for the said shower but cannot find it ? It should have a warranty on it so call Triton customer service . Regards kop

 

[Andymoz]

Does it slam then go cold it could be a faulty cartridge in the shower I have searched for the said shower but cannot find it ? It should have a warranty on it so call Triton customer service . Regards kop

KOP I suspected a faulty cartridge, which is why I changed the shower. The shower is located within a stud wall with just enough room to swap over the shower body, defiantly no room to change fixed pipework. Therefore due to obsolescence, admittedly I had this new shower off eBay (sold as new - not fitted). It could be the thermostatic cartridge, which would mean that both my original Triton Alcor and the new Triton Thames cartridges are faulty? Unfortunately these are at least £100, but I guess the only way to find out for sure? I've attached a couple of shower images. Really appreciate the chat, thanks. Andy

 

[Brambles]

It could be a restriction on the cold feed to your shower. In a thermostatic shower as it gets hotter, if there is no or insufficient cold feed to the shower the thermostatic cartridge will restrict the hot flow in an attempt to hold the temperature at the set level.

Thermostatic showers can do strange things if the hot and cold feeds are at significantly different flow rates.

An indicative test for a weak cold feed, but not conclusive is to turn the shower to maximum hot and run it - the shower should run for longer before the problem occurs. If you can set the boiler
temperature below the set shower temperature, even better the test is more conclusive.

It is a pain, but removing the shower valve and testing the hot and cold dynamic feed pressures and flow is the only sure way I know of to isolate exactly where the problem lies.

Flexi connections are not ideal, even if they don’t appear twisted, they can be problematic.

Earlier this year, I had a Grohe shower on an unvented system displaying similar behaviour. A plastic cover from within the combination valve ( at the UV tank) had detached itself and was restricting the cold flow. Hardly noticeable at the cold tap - but very noticeable at the shower.

Good luck

 

[Andymoz]

It could be a restriction on the cold feed to your shower. In a thermostatic shower as it gets hotter, if there is no or insufficient cold feed to the shower the thermostatic cartridge will restrict the hot flow in an attempt to hold the temperature at the set level.

Thermostatic showers can do strange things if the hot and cold feeds are at significantly different flow rates.

An indicative test for a weak cold feed, but not conclusive is to turn the shower to maximum hot and run it - the shower should run for longer before the problem occurs. If you can set the boiler
temperature below the set shower temperature, even better the test is more conclusive.

It is a pain, but removing the shower valve and testing the hot and cold dynamic feed pressures and flow is the only sure way I know of to isolate exactly where the problem lies.

Flexi connections are not ideal, even if they don’t appear twisted, they can be problematic.

Earlier this year, I had a Grohe shower on an unvented system displaying similar behaviour. A plastic cover from within the combination valve ( at the UV tank) had detached itself and was restricting the cold flow. Hardly noticeable at the cold tap - but very noticeable at the shower.

Good luck

KOP I suspected a faulty cartridge, which is why I changed the shower. The shower is located within a stud wall with just enough room to swap over the shower body, defiantly no room to change fixed pipework. Therefore due to obsolescence, admittedly I had this new shower off eBay (sold as new - not fitted). It could be the thermostatic cartridge, which would mean that both my original Triton Alcor and the new Triton Thames cartridges are faulty? Unfortunately these are at least £100, but I guess the only way to find out for sure? I've attached a couple of shower images. Really appreciate the chat, thanks. Andy

Does it slam then go cold it could be a faulty cartridge in the shower I have searched for the said shower but cannot find it ? It should have a warranty on it so call Triton customer service . Regards kop

KOP Sorry I didn't fully answer your previous question. Yes the shower does appear to slam shut, then pulses cold due to loss of demand and the boiler flaming out.

 

[Andymoz]

It could be a restriction on the cold feed to your shower. In a thermostatic shower as it gets hotter, if there is no or insufficient cold feed to the shower the thermostatic cartridge will restrict the hot flow in an attempt to hold the temperature at the set level.

Thermostatic showers can do strange things if the hot and cold feeds are at significantly different flow rates.

An indicative test for a weak cold feed, but not conclusive is to turn the shower to maximum hot and run it - the shower should run for longer before the problem occurs. If you can set the boiler
temperature below the set shower temperature, even better the test is more conclusive.

It is a pain, but removing the shower valve and testing the hot and cold dynamic feed pressures and flow is the only sure way I know of to isolate exactly where the problem lies.

Flexi connections are not ideal, even if they don’t appear twisted, they can be problematic.

Earlier this year, I had a Grohe shower on an unvented system displaying similar behaviour. A plastic cover from within the combination valve ( at the UV tank) had detached itself and was restricting the cold flow. Hardly noticeable at the cold tap - but very noticeable at the shower.

Good luck

Wish I'd posted this prior to re-tiling the shower, therefore unable to access the flexible pipes to carry out the pressure test, but agreed this potentially could be the issue.
I'm not home until the weekend, but will carry out the above test with shower on full temp / boiler on min temp.
Additionally I've ordered a new thermostatic cartridge, expensive but at least it will answer the question.
Will post back in a couple of days.
Many thanks

 

[Andymoz]

Gents, just wanted to say thanks for your posts.

To absolutely rule out the thermostatic cartridge, I decided to buy a new one direct from Triton, however the problem remains. I also tried Brambles suggestion, but even with the shower temp at max, and the boiler temp at min the shower shuts off, which intern cuts out the boiler.
Regardless of shower / boiler temperature settings I am unable to open the shower supply Vv past half way, if opened further the shower slams off immediately.

To conclude, from the comments, it looks like the problem may be due to a restriction in hot or cold feeds, but with limited access to pipework / flexibles, looks like I'm going to have to live with the issue.

Thanks again

Andy

 

[Stigster]

Is the valve mounted in studwork? If so can you access it from the other side by cutting out a section of plasterboard? You could find an appropriately sized access panel, cut out to that size and work on the valve/flexis from there which would be my preference, or just make good with another cut of plasterboard and redecorate after you've fixed the problem.

This all depends upon what's on the other side of the wall and its construction method of course.

 

[Andymoz]

Is the valve mounted in studwork? If so can you access it from the other side by cutting out a section of plasterboard? You could find an appropriately sized access panel, cut out to that size and work on the valve/flexis from there which would be my preference, or just make good with another cut of plasterboard and redecorate after you've fixed the problem.

This all depends upon what's on the other side of the wall and its construction method of course.

Stingster,
Great suggestion, unfortunately in my case the shower valve is located within a false bulkhead against a brick wall. Many thanks all the same.