Slow hot/tepid water in new house

[Fuckedoffat48b]

We moved into a house a week ago and have had problems with the hot water.

1. It takes ages to come through 'hot'
2. And when it comes through it comes through it comes through very tepid/cool.
3. You can make the water hotter by turning the tap/shower down to an (unusable) trickle
4. Occasionally the boiler doesn't come on when the shower is turned on, but does when the tap is on it does.
5. One side of the shower piping heats up, even when the water is only coming through very tepid.

We had a full structural survey and also had the boiler serviced (don't ask) and both noted it was very old, over 15 years, but stated it was working.

I spoke to a plumber who said the system had too much lag, and he could fit a pump or a return. However, would getting a new boiler sort this problem out, or is it a specific plumbing issue.

have you got a cylinder?

@pigletjohn What is a cylinder? I don't think so. It is a combi boiler, no tank.

if you don't have a hot-water cylinder, then I don't see that you can use a pump to keep the water in the pipes hot. Anyway, that method is wasteful of energy, because the pipes act as long, thin radiators and the boiler has to keep running to maintain the heat.

Fill a bucket at the hot-water tap in your kitchen sink. Time it. How many litres per minute does it deliver?

Now do the same with the cold water tap at the kitchen sink.

What are the lpm figures?

Are you in a hard water area?

How old is the boiler?

p.s.

Note that I am not, yet, interested in the shower.

If the supply at the kitchen taps is acceptable, we can look for a fault in the shower mixer later.

@pigletjohn the pressure in the taps is fine. The boiler is 'over 15 years old' according to both surveyor and gas engineer who looked at it. We are in a v hard water area (SE London). The problem with the hot water coming through is in both the taps and the shower.

It took 1.08 minutes to pour 12 litres from the hot tap and 0.34 minutes to pour 12 litres from the cold tap.

the flow through the hot tap is adequate for a shower, so it does not seem blocked with scale. Did it seem fully hot? Most combi boilers are capable of providing 12 litres of shower-hot water per minute, if performing correctly.

No, it is tepid whether it comes out of any of the taps or shower @pigletjohn

Can you look at the dials, post a pic, is it all set correctly, have you topped up the water level. What sort of shower is it.

if it is tepid even out of the kitchen taps, or a non-mixer tap, then you have a boiler problem.

You can try turning the flow rate down, and see how hot you can make the water come out of the tap (with a combi, less flow means higher temperature)

After doing that, turn on a (non-mixer) cold tap and see if the temperature from the hot tap changes.

Mixer taps make it a bit harder to work out what's going on, because you may not be able to tell if the mixer is adding cold water to the mix, or if you are just looking at the hot water. That's why I am not looking at the shower mixer yet.

You should hear the boiler start up and run at peak power (rather noisy) when you turn a hot tap full on, especially the bath tap, which probably has the greatest throughput.

If you can find the make and model of your boiler, we can see what its power is. A modern combi is usually around 30kW.