Shower not piping hot anymore

[dalboy]

hi guys

i have an en suite shower that has been fine for months (moved in jan).

now it doesnt get hot when i put it to max. it goes cold when moving the mixer to the right as normal. turn it left for heat and it gets hotter but from halfway to the end it doesnt increase in temperature.

i have a combi boiler and all hot taps in the house are piping hot, including the sink next to the shower. if i turn on the cold tap on the sink, the shower gets hotter, or if the toilet is flushed the shower gets hotter.

i managed to speak to the shower unit support and they are adamant the thermostat is ok and that i need a PRV attached to the cold water mains as its too high. Nothing has changed though which is what is odd? Cold water at the tap in kitchen seems the same it has always been.

the pipe work for the mixer shower is behind the tiled wall - i managed to take the mixer plate off (with mains water off obviously) and flushed the pipes as stated on the shower unit website, but the problem persists. combi heats up and lights up as usual when the shower is running.

any advice guys before i get a plumber out?

thank you!

 

[Madrab]

Where is the hot and cold shower water delivered from? Cold cistern/hot cylinder, combi hot/mains cold, unvented hot/mains cold, cold mains/hot cylinder??

 

[dalboy]

hiya

its from the combi hot/mains cold.

also to add I done the "reset thermostat" on the mixer shower as told to do my the manufacturer which didn't make a difference - turn all the way to cold until you hear a click, then slowly turn to hot

 

[dalboy]

any ideas guys? much appreciated

 

[Madrab]

Do you have a PRV before the combi to reduce the inlet pressure to the boiler?

 

[dalboy]

Not that I know of.

Ill take a picture of the piping under the boiler tonight.

Thing is, if there was which I don't think there is, wouldn't this affect all hot water including the taps (which all are piping hot)

 

[Madrab]

The fact that when you turn on the cold water on the same pipe run it then allows the shower to run hotter suggests that the cold pressure is higher than the hot and it's restricting the hot water at higher flow rates within the mixer which could rule out the thermostat. That being said is there a filter on the on the thermostat and has that been cleaned? What's the make of shower?

 

[dalboy]

Thanks for the quick response.

The shower is this one:

http://www.hudsonreed.co.uk/products/showers/kubix/triple-concealed-thermostatic-shower-valve-A3014

I cant see a filter on the thermostat.

Here is a picture I took - part of the body looks eroded / chipped but I cant see if this would make a difference as turning between hot and cold still works.

http://postimg.org/image/b3c5l0bn5/

 

[Madrab]

Have you removed the strainers/check valves and made sure they aren't blocked & cleaned them out? Numbers 5/6 in your parts list.

Strange why the body would be chipped though as you say I don't think that's intrinsic to its operation

 

[dalboy]

No I haven't cleaned them - My knowledge is fairly limited with this kind of thing.

I only removed the sealing screw to drain out and check if there was a blockage, then turned on mains water briefly to flush it - which it came out at a good pressure with no obvious blockages. As its plumbed into the wall I didn't realise you could then dismantle it further to get to the strain valve. Maybe ill have to re-visit this when I get a chance.

Can I rule out the combi boiler completely seeing as hot taps in the rest of the house are fine?
Would a PRV resolve the issue? just seems odd why all of a sudden the issue has appeared.

Thanks again - its really appreciated!

 

[Madrab]

Be careful then Dal, if you're at all unsure then I don't recommend that you start to dismantle things and get someone in.

Given you have good hot water everywhere else and this hasn't changed recently then it suggests your boiler is fine.

If your shower was fine before and now it's not then there are only a few things that would normally cause a hot water pressure imbalance in the mixer, which is what the symptoms suggest is going on

• Blockages/restrictions on the hot side of the mixer - Check and clean the strainers/check valves - pull the thermostat out and check it's clean etc.
• Thermostat no longer efficient - though given hot increases when cold tap is opened elsewhere does suggest that it's not this
• Increased cold pressure through the mains - PRV may help with this but pressures need to be tested 1st to see if the mains pressure has increased.

These are the things I would run through 1st to fault find your issue.

 

[dalboy]

Thanks a lot. Think I will get someone in - Just wanted to be a bit more clued up beforehand.

The thermostat cartridge in my above picture - it seems its fixed securely as I was looking at the manual about cleaning it / removing it but couldn't understand how this was done? any ideas?
Also the two sealing screws for hot and cold water - how tight / loose do these need to be? I even tried tightening the cold one to stop cold water coming in just to see if the hot stayed hot, but it didn't. Guess work on my half I guess!

 

[Madrab]

Number 12 in your manual is the retaining nut, it has slots in it that you use a tool to loosen. Usually I'd be using a screwdriver and a light hammer and tap the retaining nut round till it loosens.

The sealing screws will just be nipped up, they wouldn't usually alter the water flow.

 

[dalboy]

Thought I would update this before I forget as it may help others.

Decided to have another look at this yesterday. Turned off mains water and stripped it all back. Got to thermostat, undid retaining nut then managed to remove thermo with a bit of force. Checked it over and couldn't see any debris or anything obvious that would cause an issue - shone torch down it etc...

Checked hole where it sits and also looked pretty clear - used a cloth to clean it out and made sure hot and cold into the hole felt clear (couldn't see up and down them due to location)

Put it all back together and turned tap all the way to right until you here the click to reset thermo.

Turned on mains water.

Turned on shower. Cold water as it should. Slowly increased temperature and boom piping hot water!

Left it run for a good 5-10 minutes to see if it fluctuated but no seemed fine.

So will keep an eye on it this week.

Still none the wiser as what the issue was - maybe there was something causing a blockage but it definitely wasn't obvious.

Thanks for your help Madrab.