Boiler issue - any ideas what's wrong?

[tiba]

Moved into new house (old Victorian terrace)
It has a baxi combi boiler.

Before moving in we had boiler serviced by engineer. All fine.
It seems to be working a great with the radiators along with kitchen hot tap and bathroom sink hot tap.

However, when running shower or bath hot tap the boiler makes a horrendous noise and if hot tap turned on fully the water does not come out hot but luke warm to cold.

To get the bath running hot I have to leave it on a trickle.

Any idea what this could be?

What's the pressure set to?

How old is the boiler? My plumber says that any modern style boiler over 6 years is due for change.
He says they've are just so highly strung that their need updating regularly.
In my last house boiler was 30 years old and still going strong but modern combis too technical.

Sorry, meant to say get a good plumber out. Simple.

What is the pressure gauge showing, what temperature is the hot water set at and is the filling loop tap actually closed? We had a Baxi combi in our old house and the only time it made a terrible noise was when the filling loop hadn't been closed properly and it was way over pressure. It was banging away like nothing on earth. Didn't need a plumber to fix it. If you don't have the manual you can find it online and have a look in the trouble shooting section. If you can't sort it out yourselves then call a plumber - a gas safe one.

Pressure good (just over 1 bar)

Temp set to max

Boiler is approx 10 years old at a guess.

Have called our plumber but he isn't back from holiday until next week.

I'm assuming I should really get a boiler engineer out instead.

Hoping it doesn't need replacing as on maternity leave 😬

This is pressure gauge reading

it's a combi boiler....what more do you need to know?

we had one! ...it was the bane of my life, always breaking down, losing pressure and generally being an utter pita, like some ungrateful old relative always trying to get the upper hand by being difficult.

My parents moved into a new build in 2002/3 ish, and are on their 3rd already....that's a brand new build, all insulated, two bed bungalow so it's hardly being overworked.

It's a Baxi though - they are a good make. The water temp doesn't have to be set to max - it's can cost quite a bit more to have the temperature up really high. With a combi you need to reduce the flow to get really hot water so you don't turn the hot taps on fully or you'll get lukewarm water; that's just how they work. You're sure it's the actually boiler making the noise, not the pipes?

For a gas boiler you need someone gas safe registered to look at it. If they are not gas safe registered they shouldn't do any work on it. I'd get the engineer who serviced it back to it.

My god I had a baxi boiler also in an old property. First it was the diverted valve and then later it was the heating plate. Eventually just got the bloody thing replaced!

popcorn - how much should I expect to pay to have it replaced?

wowfudge - definitely the boiler making the noise.

Il get back the boiler engineer who serviced it and fixed it last time (he's been out to us 3 times already since April to see to it )

Noticed another strange occurrence - when the bath/shower is running the bathroom towel rail gets hot.

The rest of the radiators in the house do not.

I'm not too sure if this is how it's meant to work so that you still get warm towels when the thermostat is turned down or if this is a weird anomaly that shouldn't happen

"if hot tap turned on fully the water does not come out hot but luke warm to cold.
To get the bath running hot I have to leave it on a trickle. "

that's because it's a combi.

A combi has no stored hot water, it can only raise the temperature of (X litres of water per minute) by (Y degrees)

If you increase X, Y falls.
If you decrease X, Y rises.

If it is an old or low-powered boiler, X and Y may be quite low numbers. Or there might be a fault.

If you tell us what X and Y are, we may have further ideas.

I have reduced boiler water temp just now.
It was previously turned nearly up to max at 70 degrees. I have now turned it down to 54 degrees.

Boiler is no longer rattling and making banging noises.

I can turn tap on further than I could before (but not up to max)

"rattling and making banging noises"

these might be due to limescale or dirt clogging the heat exchanger and causing bubbles of boiling steam. A competent engineer can easily verify it. Depending on age and condition it may be a worthwhile repair.

It is very unusual with a combi to have a towel rail that heats up when you run hot water. It might intentional, or a design error, or a fault. Turn it off at the knobs and see what happens. If some other radiator now heats it, there is a common fault.

Run the kitchen tap for the same length of time you run a shower/bath for and then check that Towel rail again. The boiler knows only that there is a demand on the hot water not which tap it is coming from.

I suspect the diverted valve is letting by so some of the output from the boiler is lost to the radiator circuit causing a lower temperature at the hot tap.

Diverter valve not diverted