Hot water in cold water tank in loft
Discussion
I’ve just noticed that the cold water taps on the bath and basin have warm water coming from them. The cold taps elsewhere in the house are cold. I think these are fed directly from the mains. I’ve checked the cold water tank in the loft and this has warm water in it.
The water / central heating system is gas powered, vented(?) and I have a hot water cylinder. Immersion heater as a back up, but this is switched off and in any case doesn’t work.
A quick google throws up possibilities such as a cracked heating coil in the cylinder, blocked valves and faulty mixer taps. I do know that the shower has a faulty thermostatic mixer as it’s not been very controllable for a while. Checking the shower now I see it has the same problem as the bath and basin as it has hot water when just cold is selected. I’d thought this was just an inconvenience and that it only affected the shower, but could this be the cause of the problem?
The water / central heating system is gas powered, vented(?) and I have a hot water cylinder. Immersion heater as a back up, but this is switched off and in any case doesn’t work.
A quick google throws up possibilities such as a cracked heating coil in the cylinder, blocked valves and faulty mixer taps. I do know that the shower has a faulty thermostatic mixer as it’s not been very controllable for a while. Checking the shower now I see it has the same problem as the bath and basin as it has hot water when just cold is selected. I’d thought this was just an inconvenience and that it only affected the shower, but could this be the cause of the problem?
Err ... to heat the cold water tank appreciably you must be dumping a lot of hot water into it from somewhere. I'm no plumber, but I've seen systems where the vent pipe from the hot water cylinder would empty back into the cold water tank, but the cylinder is usually fed from the tank by gravity so you'd never get a huge flow into the cold tank that way, surely?
If the heat exchanger in the hot water cylinder had cracked, then water from the primary circuit (at least initially loaded with rust inhibitor, rust and gunk) would be mixing with the water in the tank and coming out the taps. Nice. I suppose if the primary circuit was somehow refilling itself from a mains pressure supply, that would allow a load of water to get ejected into the cold tank in the loft. But that doesn't sound very likely.
If the heat exchanger in the hot water cylinder had cracked, then water from the primary circuit (at least initially loaded with rust inhibitor, rust and gunk) would be mixing with the water in the tank and coming out the taps. Nice. I suppose if the primary circuit was somehow refilling itself from a mains pressure supply, that would allow a load of water to get ejected into the cold tank in the loft. But that doesn't sound very likely.
Taps affected definitely fed from the tank in the loft. The water in the tank was pretty warm so there certainly must be a lot of hot getting in there somehow.
I've played around with the shower mixer, worked it back and forward, tapped it etc. The hot water is switched on and the cold has returned to normal. I’ll pick up a new shower mixer bar in the morning, fit that, and then see if it’s sorted. If not I’ll at least have fixed the dodgy thermostatic valve I should have looked at ages ago, and call a plumber.
I've played around with the shower mixer, worked it back and forward, tapped it etc. The hot water is switched on and the cold has returned to normal. I’ll pick up a new shower mixer bar in the morning, fit that, and then see if it’s sorted. If not I’ll at least have fixed the dodgy thermostatic valve I should have looked at ages ago, and call a plumber.
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