Baffling Thermostatic Shower Valve Problem

[bodger1]

Spoke to the manufacturer they've told me to take off the none return valves, remove the plastic section inside and then replace it - something to do with the water pressure not being high enough!? This doesn't exactly sound right as then there'll be nothing preventing back flow, but I'll try it and see.

 

[Technotim]

You are gravity fed both sides of the valve therefore you should have the same flow/pressure give or take a tad hot and cold, removing the non return valves will not suddenly give you cold flow if you are getting hot you should have cold. if any thing you will get a slightly better cold flow as there is less resistance generally on that side.

baring airlock in the cold side.

If you know you have flow on the cold as you said you have tested the water flow then you have a faulty cartridge a stuck nrv(very common) or the filter is blocked, I bet faulty cartridge as the hot should shut down with no cold water coming through.

If you call Ultra Ask for Alison or Eileen on the customer care helpline they will send out a new cartridge as this is not the first time this has happened.

The Idea of removing the cartridge to see if you have a cold flow is a good one, It has been known for a brass body to be not drilled out properly and it gives you a difinative answer if you then have cold water flowing then its not the NRV and its not the filter and the body is fine it is then the cartridge.

When it comes to removing the NRV's its standard answer for them re pressure problems most people expect a decent shower when a manufacturer states 0.1bar pressure for the Valve that is the absolute min for a trickle of water, then you fit a shower head and you water slows down even further.

p.s its easy to remove the cartridge take off the temp handle remove the temp stop device (bit 'o' Plastic) turn off water supply, unscrew large nut anti clock wise. cartridge is out.

 

[bodger1]

Thanks Technotim. Probably wont look at it until the weekend, but will let you know how I get on.

 

[alexeix]

Hi All,

I know it's been a while since this post was raised, but what was the cause of the problem?

I have the same issue, except the hot water is affected, not the cold.
I know it's not caused by the pipes being fitted incorrectly, because this is a secondary problem.

This is a thermostatic shower working on mains pressure, from a condensing combination boiler.

After fitting, the shower worked fine for approximately 18 months, however, I then started seeing a reduction in pressure on the hot water side - I could tell this because when running the shower as hot, the boiler did not 'fire up'.

The hot taps in the kitchen, bathroom basin and hot water tap (plus mixer), were all working fine and gave me hot water!

After a Worcester Bosch engineer confirmed that there was no problem with the boiler (fitted when the system was installed), and specifically with the heat exchanger, I obtained a replacement thermostatic valve from the supplier, after going through their checks.

I replaced it, but now the hot water flow from the shower has been reduced to a trickle/a few drops!!
As before, all hot taps (and the bath mixer) provide hot water.

I'm also wondering if there could be some kind of air lock, but I don't see how that could be possible.
Any ideas?

I'm going to try turning the thermostatic valve tonight, as already suggested earlier in the thread.

Thanks in advance for your advice.

 

[alexeix]

No suggestions around the cause/solution?

I can't seem to find a plumber to come and look at this, so I'm currently stuck.

In case there was air trapped in the system, I turned off the water supply at the stopcock, turned off the boiler, partially unscrewed the thermostatic valve, turned the water supply and boiler back on (so there was water coming out around the valve), turned on the shower (the flow was still bad), then screwed the valve back in.
I think that this should have cleared any air from the hot water pipe.

Result: the problem still occurs - insufficient flow of water from the hot supply to fire up the boiler...very little water comes out when the shower control is turned up to the hottest (override button pressed).
The cold supply is very good.

I get hot water from the kitchen tap, the bathroom basin and the bath tap, without issue.

 

[alexeix]

Problem solved and I'm posting the answer here for any other poor sods who encounter the same issue.

My shower has a non-return valve on the hot water pipe, right before the thermostatic shower valve.
There is also a rubber washer which contains a very fine mesh - presumably to stop gunk clogging up the thermostatic valve.

This mesh was almost completely filled with a big plug of limescale, hence the reduced hot water flow and the fact that the boiler was not getting sufficient flow to fire up.
There was also some scale inside the non-return valve.

To resolve the problem, I removed the plug of scale from the mesh filter and cleaned it.
I then poured a dilute solution of vinegar into the non-return valve and left it for a few minutes, so that it dissolved the remaining scale.

I rinsed it out with clean water, replaced the non-return valve and washer/filter, then re-assembled the shower valve.
Hey presto, when I turned the water back on and tried the shower, the flow is good and the water is hot!

I only found out about the non-return valve, because I called the supplier of the thermostatic valve and asked what else it could possibly be. They didn't mention it when I originally called and so now I have a spare thermostatic valve for my troubles.