Not hot water from bath tap

[mcdous]

I have a combi boiler and constant hot water out of all my taps apart from the bath tap. Even running it at a trickle will not produce anything other than luke warm water. My shower, which is a mixer tap attached to the bath, produces water at a good temperature so I'm unsure why the actual taps do not produce the same. Can anyone suggest what the problem may be and if it would be expensive to fix? Thanks

[buildersmate]

As you know I am sure, combi boilers act as suppliers of hot for the CH and instantaneous water heaters. Thae rate at which you can draw hot water off the system is governed by the capacity of the boiler.

A couple of questions. Does this problem only occur in the winter when you have the CH on? If it does, it suggests to me that the capacity of the boiler is not big enough to heat the water at a rate to feed your bath.

If not the above, has this got worse gradually over time? If so, the problem is probably caused by scale, making the pipes smaller in diameter on the inside and limiting the capacity of the system to transfer heat through the limescale. If you run a lot of baths, this could happen over time. Do you live in a hard water area (south of line joining Exeter to the Wash)? More liklihood of scale. You can descale the system yourself - investigate Fernox or Sentinel products at plumbers merchants or the larger DIY sheds.

[mcdous]

Thanks for your response. To answer your questions, This is a tenement flat in Glasgow and it was ok when I moved in May. The CH is kept on at all times (summer or winter setting) and the hot water part of the boiler has been on full since May, but the water temp gage is defo showing much less than it did in summer months. I have only had a couple of baths since movig in and then suddenly there seemed to be this problem. I did have an issue with a leak in my boiler in Oct which affected the pressure at the time and no idea if it is related to that, but the water has been barely luke warm since then.

[stanleyman]

If you have a hotwater thermostat on the boiler make sure it is turned up and also you have sufficient pressure in the system. Some combi boilers can only supply 8 or 9 litres of hot water per minute but in the winter the incoming, water being much colder, can't heat as much and this will be more noticeable when filling a bath.

As buildersmate has mentioned it can also be limescale build up in the heat exchanger needing treatment with a good scale remover but this isn't really a diy job and could mean a new heat exchanger.

The problem could also be related to the bath taps if they are of the mixer type with an internal leak from the cold or you could have a safety mixer fitted underneath to prevent scalding water at the bath taps that may need resetting or descaling. If all other taps can supply lots of hot water then this could well be the problem.