Thermostatic Bath/Shower - Hot Water Problems

[Skutter]

1) Boiler make / model (gas or oil)

Gas Open System

2) What is / is not happening

i) Hot water to shower/bath can take up to 2 to 3 minutes to appear
ii) Hot water input/overflow tank can overflow at various times sometimes coinciding with using bath/shower

3) Has ANYTHING else been done / changed recently

New tank 6 months ago

4) When did it (problem) start

Thermostatic Bath/Shower taps are new as part of a new bathroom installation.

The overflow did happen at various times (not regularly) before eiether the new bathroom or the new tank.

5) When does it happen? eg, heating coming on or going off

Various ... overflow "can" coincide with using bath/shower but sometimes happens independantly, taking a bath/shower does not automatically lead to an overflow.

6) Anything else you feel may be of relevance

Hot water pressure is reasonable in bathroom approx 3/4 that of cold.

Any help gratefully received ...

 

[Paul Barker]

Fine the hot water if it hangs around so long in future.

Get the float valve checked.

 

[Skutter]

Having turned down the cold water pressure upstairs a tad more the problem has not happened this week... hot showers straight away and no overflow.

My worry is this (don't laugh as I really haven't a clue how such a device works ) ... is it possible for the Thermostatic valve to allow the cold water to start to push back into the hot water supply to the bath/shower when it is switched off?

Cheers

 

[Skutter]

had the first overflow for a week ... only change I can see is that its colder so the heating kicked in fully.

I'm now v confused

 

[breezer]

as Paul Barker said, check the ball valve.

The reason a tank over flows is because too much water is getting in, as the water comes in via the float valve, this is wht you need to check adjust or change

 

[ChrisR]

is it possible for the Thermostatic valve to allow the cold water to start to push back into the hot water supply to the bath/shower when it is switched off?

Yes it's common. H and C to shower shouldlhave non return valves.

Is there a pump on the shower supplies?
Is the cold from the mains?
Is the hot from a combi or a HW cylinder?

 

[TicklyT]

It sounds like it it could be the cold water passing back through the mixer valve.
You say you turned down the cold water pressure. If you have just closed the stopcock/service valve a bit, this will only reduce the flow rate. The static pressure will be exactly the same. It may mask the problem, but will not cure it.

Have you got a non return valve fitted in the hot feed to the mixer?
you could try shutting the service valve on the hot side of the mixer when an overflow occurs, and see if the overflow stops. this could indicate water backflowing through mixer

Does the float valve continue to run/drip when the CWS tank is full?

You may see a limescale witness mark around the tank at the normal full level. Is this at or very near the overflow level? The float valve should shut off when the water is a couple of inches below the overflow outlet. The float level may need adjusting. The float valve may dribble a bit for a couple of minutes as the level reaches full, but should shut off completely within, say, five minutes. If it continues, then there may be a bit of grit in the valve seat, or the seating may be worn. Try cleaning/changing the valve and seat

 

[Skutter]

Great feedback thanks ... I'm sure the float valve is fine there is the slightest of drips but that is all.

Will spend the weekend trying to recreate the problem and repost if I get anywhere (happens first thing in the morning when usually on way to work hence why I'm a bit vague at the moment).

In answer to questions so far:

Is there a pump on the shower supplies? No
Is the cold from the mains? Yes
Is the hot from a combi or a HW cylinder?H/W cylinder


Many thanks for your time all.