Combi Boiler Help

neilmcl

AbbyCarr98 wrote: »

The bath has a hot and cold tap but the water is mixed. If I just run the hot, it runs scalding and then freezing cold. I assume the shower is not electric as the boiler comes on when the shower is running.

How long do you run the bath tap before giving up, try running it for a few minutes to see if it eventually heats up. It does sound like the flow to the bath tap is too high for the boiler to cope with.

AbbyCarr98

We've run it for around 5 minutes. After around 30 seconds the water is scalding, stays that way for perhaps a minute or even two and then freezing cold. How can we rectify the situation? Can we not have a bath? As previously said, if I run the tap slower it doesn't make a difference and the shower runs water faster than the bath taps. The previous owner had 2 small children so I cannot imagine they just went without a bath. The bath is newly fitted but had a bath previously in the house which I assume they would have used.

neilmcl

Take the side of the bath and have a look at the bath tap connections and pipes and see how the shower and basin taps are fed. Might be worth posting up some pics as well.

AbbyCarr98

As someone who is not particularly strong on DIY, it is probably not wise I try do this. It isn't a typical plastic sided bath, it appears to have been tiled in so I don't know how feasible that ever is. Would it be worth trying to find the warranty on the bathroom and getting the company to check it?

Hasbeen

AbbyCarr98 wrote: »

Hi, I do not know if the shower is electric. How would I know? We didn't have the bathroom installed, it was the previous owner. Just tried running bath taps now. Boiler light comes on, hot water comes out. Cold water then starts running but boiler light still on and no fault codes on it. Running the bathroom tap at the same time, stops it going freezing cold but it's barely lukewarm I would say when both running. Our bathroom taps will run scalding for as long as we would want, they never run off cold and they're not electric

Confused about above, bathroom taps are barely lukewarm but they run scalding for as long as you want? Please clarify.

If shower is electric there should be a ceiling switch in bathroom or a wall switch outside bathroom door to turn on/off. You can also try turning boiler off and see if you still get hot water at shower.

Combis are usually fed with 15mm cold water copper pipe. Baths are fed with 22mm copper pipe. Usually plumber will put in restrictor on the hot 22mm or even step pipe down to 15mm. So flow into boiler and out to bath are the same rate. If 22mm then water will not have a chance to heat up going through combi.

Have you checked hot water setting is turned up to full at combi? There is usually a setting with Radiator symbol and one with taps symbol.

As others have said crack open the hot water tap at bath to get a minimal trickle and see if its hot. If not then you need to get boiler checked out.

AbbyCarr98

The bathroom taps run scalding hot whenever we want them. As in the taps on our bathroom sink. Our bath taps, run scalding for around a minute or too and then go freezing. A previous poster advised trying to run the bathroom taps at the same time as the bath taps. When I did this, the bath taps didn't go freezing cold then went lukewarm but on the cold side of lukewarm.

The shower isn't electric then, it's gas powered. But particularly powerful and it has one of those large waterfall type heads. So the flow is pretty rapid. I assume we could try fill the bath with the shower head, it would be quicker but obviously this isn't the point of having a bath.
I changed the setting on the boiler previously as it was on Eco, and now have it on the highest. Our showers are lovely and hot, I like them scalding. All the taps produce this scalding water too, and they don't ever turn cold they stay scalding hot it's just the bath that stops after a minute or so. Everything else runs perfectly and stays hot and runs for as long as we want them to.
If we run the bath a trickle or on full flow, it doesn't make a difference. The water starts to run scalding after 30 seconds or so, runs scalding hot and then freezing after a minute or two. I can't decide if this is a plumbing problems or a job for a boiler engineer.

Alex1983

As a rule if you can get good hot water at some outlets but issues with just 1 then the problem is unlikely to be the boiler and more likely the tap or pipework to the tap.

Hasbeen

AbbyCarr98 wrote: »

The bathroom taps run scalding hot whenever we want them. As in the taps on our bathroom sink. Our bath taps, run scalding for around a minute or too and then go freezing. A previous poster advised trying to run the bathroom taps at the same time as the bath taps. When I did this, the bath taps didn't go freezing cold then went lukewarm but on the cold side of lukewarm.

The shower isn't electric then, it's gas powered. But particularly powerful and it has one of those large waterfall type heads. So the flow is pretty rapid. I assume we could try fill the bath with the shower head, it would be quicker but obviously this isn't the point of having a bath.
I changed the setting on the boiler previously as it was on Eco, and now have it on the highest. Our showers are lovely and hot, I like them scalding. All the taps produce this scalding water too, and they don't ever turn cold they stay scalding hot it's just the bath that stops after a minute or so. Everything else runs perfectly and stays hot and runs for as long as we want them to.
If we run the bath a trickle or on full flow, it doesn't make a difference. The water starts to run scalding after 30 seconds or so, runs scalding hot and then freezing after a minute or two. I can't decide if this is a plumbing problems or a job for a boiler engineer.

Showers are fed by the smaller 15mm pipes also bathroom sinks are 15mm. As said baths are usually the bigger 22mm usually stepped down to 15mm, if using a combi. But simple test is to run hot bath tap at a trickle to clarify.

As you have stated this is not working, but all other taps are scalding. It does look like a problem with the pipe to your bath hot tap or the bath taps themselves. PLUMBER required for that if no hot water to bath tap. Central heating engineer if no hot water to anything.