Bath water not hot enough

[ZedTheRed]

Hi All,

I'm hoping someone can help me.

I get piping hot water in the kitchen and bathroom basins. However in the bath I only get warm water and don't even have to use the cold. I have always had this problem since I moved in 6 years ago but had an electric shower so wasn't a problem.

I have now had a thermostatic mixer shower installed and if I have it at the hottest setting it is fine but I know in the winter months It would need it to be hotter.

Every plumber I have asked say I need a new better boiler as mine is too old and hasn't got enough capacity. The bolier I have is a Biasi Prisma 24SE and is a combi. The reason I'm not convinced is that it works perfectly well apart from the bath so how could it be the boiler. I live in a 3 bedroom house with a kitchen and one bathroom. One plumber also said that I have 15mm pipes going into the bath instead of 22mm and that could be a problem also.

Any advice would be most appreciated.

Thanks

 

[gigz]

Close the bath tap down a bit, with a combi like yours the slower the water comes out of the tap the hotter it will get, it takes a bit longer to fill the bath though.

 

[ZedTheRed]

Thanks gigz,

I have tried that but it only makes it slighty hotter and and with a lot less flow.

 

[namsag]

Got a mixer tap on bath ,could it possibly be allowing cold into hot side.
Turn cold supply off to boiler (should be an isolating valve by boiler) and then open hot tap the water should stop running after a few seconds if it carries on running and its cold it means the tap is faulty

 

[ZedTheRed]

I turned the cold supply off to the boiler and turned on the hot water tap and a small amount of water drained out and then nothing. So does that mean cold water is not going into the hot?

 

[mlcinfl]

I turned the cold supply off to the boiler and turned on the hot water tap and a small amount of water drained out and then nothing. So does that mean cold water is not going into the hot?

Yes.

 

[Tipper]

You need to check that the thermostatic mixer is set up correctly as they are often set to protect against scalding (quite rightly) but sometimes this is too low.

If you've got the installation instructions have a read and see if you can reset it/move the control knob, to get off the upper stop to allow more adjustment. Maybe suggest this to your plumber.

Beware, leaving it too high means a risk of being scalded!

 

[Agile]

There is also the possibility that your boiler is not set up correctly or is not delivering the right amount of water.

It should give 8 litres per minute which is too hot to keep your hand under for long!

When was it last serviced or repaired by someone who would also check the performance?

Tony

 

[ZedTheRed]

Does that mean it looks like the boiler needs replacing with a more powerful one?

 

[Agile]

All it means is that the performance of your boiler needs to be checked before you can come to any ( meaningful ) conclusion.

Even the most powerful normal combi is only about 50% better than your boiler so its not going to be a massive improvement unless you get a storage combi.

Tony

 

[ZedTheRed]

To be honest it hasn't been serviced for a number of years. I had a lot of problems with it and had lots of parts changed by British Gas. Then for the last 3-4 years it's worked fine so didn't want anyone to touch it in case it had problems with it again.

I will get it looked at again.

 

[Agile]

It should give 8 litres per minute which is too hot to keep your hand under for long!

Tony

If you set the flow rate to give 8 li/min then you can see how it performs yourself.

Even more, if you have a medical thermometer then you can probably read the actual temperature of the hot water.

Not all people you might call will be able to properly check the boiler. It needs a proper pipe contact thermometer.

Tony

 

[kevindgas]

Even the most powerful normal combi is only about 50% better than your boiler so its not going to be a massive improvement unless you get a storage combi.

Tony

??
what you should say is that you can **** hotter liquid than a 24Kw combi can deliver!

OP the boiler is not brilliant and the water will only get hot within the temperature rise / litres per minute ratio. the bath should be fed with 15mm pipes when supplied by a combi, but it is probably 22mm having been converted from a gravity system in the past
this allows the water to pass through the boiler too quickly hence the lack of temperature