Thermostatic Shower Cartridge

[Diggory]

Hi there - I’ve been having some trouble with a mixer shower; no hot water.
The shower has not been used for a while - I’ve removed the thermo-cartridge and cleaned out the gritty bits.
I’ve soaked cartridge for couple of hours in a citric acid solution.
I’m now getting hot through but as I adjust the temperature it thumps (like a single water hammer) as the hot comes in.
I’m guessing it’s now moving but sticking - is there anyway I can free it off ?

I believe it’s a Trevi 300 shower.

Thanks in advance D

 

[Diggory]

I gave it another 2hrs soak - it’s marginally improved but still ‘thumping’. If I wind it (temp dial) all the way in it gets too hot, then as I back it off, at about half way, it goes ‘thump’ - the temperature drops (too cold) and the water flow notably increases.

I’m mindful that when the dial is fully assembled the rotation of movement will be quite restricted (even if I slide the red stop out of way) based on the 40degC factory set calibration. I’m getting hot flow only by going beyond the region of restricted rotation.

As I mentioned in the previous post, the shower has been unused for a good while; and I’ve assumed this was the issue. The shower was previously running from a vented boiler, loft tank and monsoon shower pump. I’ve since had a new combo-boiler fitted. Might this be causing my problem ?

 

[denso13]

Might this be causing my problem ?

Probably just worn out, new cartridge or shower valve should fix it.

 

[Diggory]

Thanks @denso13 (again).

True enough - it could be shot.

I did wonder that I’m getting hot through it now only because I can rotate it further (with dial dismantled).
And that this might be to do with water pressure / combi boiler.

Best D

 

[Diggory]

@denso13 - I’ve changed the thermo-cartridge (for a genuine new part) with mixed results.
The good; it’s smoother and the hot/cold transition ’thump’ has gone.
The not so good; the max temperature is notably cooler (tepid/warm at best).

If I turn off the cold isolation valve when shower on - the hot comes through at the v.hot temperature you’d expect.
But when I switch the cold in again, it quickly brings the temperature down to tepid again.
The H&C now are mains driven so I assumed that there shouldn’t be a significant balance issue.

Should I pull out and clean the H&C cartridges - so far I’ve only looked at / replaced the thermo-cartridge.
(And there was a bit of gritty rubbish that came out with it).

The shower was in good working order but sat unused for a good while.
It was previously running from a vented boiler, loft tank and monsoon shower pump.
I’ve since had a new combo-boiler fitted …………and now it’s playing up.

Thx in advance
D

 

[denso13]

Might the new cartridge need calibrated? Take the knob off and turn the spindle hotter by hand, then refit the knob.

 

[Diggory]

Thanks @denso13 - if I turn it all the way without the chrome handle fitted, it still doesn’t get hot enough.
The instruction booklet mentions calibration by removal of red clip and adjusting dial to get a measured 40degC then refitting.
Unless I’m missing something, that process seems to be about aligning the 40degC mark on the dial (and little red slide button).
Because it’s all held together with ‘C’ clips and grooves it feels like I can only wind it in/out by a fixed amount of travel ?

Best D

 

[oldbuffer]

Most are adjusted by:
1. Removing a stop (often plastic) which fits over the splines on the shaft.
2. Turning the shaft (often anti-clockwise) until the water temperature reaches 38 or 40
3. Refitting the clip so that it abuts another stop within the body of the shower.
4. Refitting the knob so that it "points" to a 38/40 degree mark, often a line on the body of the shower valve.

 

[Diggory]

Thanks for info on calibration I will have another look; I’m still unsure if this is the issue.
When I wind the thermo-cartridge adjustment all the way in (ignoring the 40degC mark) - it’s still tepid.
The calibration process seems to be more about aligning the dial than increasing the temperature if it’s not there.

I’m going to further dismantle the valve; it feels fine, isn’t stiff and doesn’t drip……but
- I’ll pull out the H/C cartridges and pop them in some citric acid.
- I’ll check the gear wheels to see if anything free spinning or striped.

I’m still wondering if this is a balance issue.
When the shower was previously connected to old vented boiler it had a Monsoon pump so would have had a balanced supply.
If I look at my new COMBI boiler pipework in adjacent airing cupboard, the cold feed to shower is noticeably more direct.
The instructions recommend a ‘reasonably balanced’ supply but then go on to say it can cope with 5:1.
Might this be causing an issue / could I try PRVs or similar on the 22mm supply pipes.
I’m probably going to cut into them to add some back flow check valves.

Thanks D

 

[denso13]

A combi has balanced supplies, both mains fed, doubt it's that. Do you know what pressure the mains is?

 

[Diggory]

I’m afraid I don’t know the pressure - but I think it’s reasonable.
I did measure the flow (in summer) and I think it was >10L/min.
D

 

[Diggory]

I can pick up a pressure gauge at weekend - worth doing ?