Hot water is usually the first thing to go wrong and the first thing anyone notices. A household will tolerate a slightly cool bedroom for weeks; it will not tolerate a cold shower for a morning. That makes hot-water faults the most reported and the most misdiagnosed problem in domestic heating.
R M Burn & Son Plumbing & Heating Engineers covers heating engineer work in Abbots Leigh, and the useful thing is that the exact shape of the symptom narrows the fault a long way before anyone opens anything.
The symptom tells you where to look
Hot water that is completely absent while the heating works perfectly is a different fault from hot water that runs warm, which is different again from hot water that starts hot and disappears after four minutes.
On a combi, no hot water with working heating usually points at the diverter valve or the hot-water side of the appliance. Lukewarm water often means the appliance is not reaching temperature or the flow through it is too high. Hot then cold typically means flow rate or a plate heat exchanger that is scaling up.
On a stored system, hot water that runs out quickly is about the cylinder and how it is heated: a failed thermostat, a stuck valve, a coil that is no longer transferring heat well, or simply a cylinder too small for how the household now lives. Water that never gets hot at all points at the heating source or the controls that ask for it.
- No hot water, heating fine: diverter valve or the hot-water side of the appliance.
- Lukewarm at every tap: temperature or flow through the appliance.
- Hot then cold within minutes: flow rate or a scaling heat exchanger.
- Runs out quickly on a cylinder: thermostat, coil, valve or cylinder size.
The cheap causes worth eliminating first
Several hot-water complaints have embarrassingly simple causes, and it is worth ruling them out before booking anything. A programmer with a hot-water schedule nobody remembers setting. A cylinder thermostat knocked down to a low setting. An isolation valve half closed after other work.
Scale is another common and undramatic cause. In hard water areas, the narrow passages that heat water quickly are exactly where scale forms first, and a combi's hot-water performance degrades gradually enough that nobody notices until it is bad.
Aerators and shower heads clog too, which produces a convincing impression of a hot-water fault when it is really a flow restriction in a fitting that costs almost nothing to clean.
When hot water is a heating system problem
On a stored system the cylinder is heated by the same water that heats the radiators, which means poor circulation shows up as poor hot water. If the coil is not getting good flow, or the system is carrying sludge that has restricted it, the cylinder recovers slowly however hot the boiler runs.
Heating system work covers radiators, pipework, heating controls, pumps and valves, and a hot-water complaint is often the first visible sign that one of those is failing. A pump that has weakened, a diverter or zone valve that is not opening fully, or controls that are calling for the wrong thing all produce hot-water symptoms first.
That is why it is worth mentioning radiator behaviour when reporting a hot-water fault, even though the two seem unconnected. Which radiators are slow, whether pipework has become noisy and what the pressure gauge does are all part of the same picture.
- Mention radiator performance even when the complaint is hot water.
- Note whether the fault changes when the heating is also on.
- Check the pressure gauge and whether it holds.
- Say when the problem started and what else was done around then.
The one that is not a comfort issue
Most hot-water faults are inconvenience. A few are not. Water that is far hotter than it should be, an unvented cylinder discharging from its outlet, or any sign of the pressure relief operating are safety matters rather than performance ones and should be looked at promptly.
The same applies to a cylinder making banging or rumbling noises, or any visible leak around it. Stored hot water is a great deal of energy in one place, and the safety devices exist because it matters.
R M Burn & Son Plumbing & Heating Engineers covers heating systems, boiler repair and emergency call outs in Abbots Leigh, so a hot-water symptom that turns out to be urgent can be dealt with on the same route rather than restarted elsewhere.
Related pages
Questions customers ask
Why does my hot water run hot then go cold?
On a combi, that pattern usually points at flow rate or a heat exchanger that is scaling up. On a stored system it points at the cylinder: how much is stored, how well the coil transfers heat, and whether the thermostat is calling correctly.
I have no hot water but the heating still works. What is that?
On a combi it usually points at the diverter valve or the hot-water side of the appliance. On a stored system it is more often the cylinder thermostat, a zone valve or the controls asking for the wrong thing. Either way the heating working is a useful clue, not a coincidence.
Is a cylinder discharging water something to worry about?
Yes, treat it as urgent rather than as a nuisance. Discharge from a pressure relief outlet means a safety device is doing its job, and the cause needs finding rather than the water being mopped up and ignored.
Absent, lukewarm, or hot then cold: those three descriptions point at three different faults, and saying which one you have is worth more than any amount of general description.
R M Burn & Son Plumbing & Heating Engineers takes heating engineer work across Abbots Leigh and would rather hear the exact pattern than the word broken. The contact page is the place to describe it.
