Why do I have water tanks in my attic? How does my immersion heater work and feed into the system? Is it true that the cold water from downstairs comes from the mains, and is therefore clean, while cold water from upstairs taps comes from the tank in the attic and probably has bits of pigeon or bat in it?
Thanks very much!
In: Engineering
There are various ways it could have been configured in the past, and how it could have been adapted over the years. Most likely if you have a cold water tank in the attic it will be empty and no longer part of the system. A hot water tank is more likely to still exist, and may or may not have been replaced at some point.
Basically your hot water system has two parts that don’t touch: clean water in the tank which comes out of the tap, and horrible water that circulates in a closed loop through the boiler, radiators, and a coil in the hot water tank where it heats the hot water you see. So the hot water tank has a cold supply in the bottom to provide pressure/keep the tank full, a coil to provide heat from the boiler, an electric immersion heater element near the top to add extra heat/as a backup (optional), and a pipe coming out of the top and going to your taps, shower etc.
There are valves which divert the closed loop water from the boiler to the tank and/or radiators depending on demand. The exact setups of these vary.
Houses in the UK generally have one of two water systems. Some have a tank somewhere high up storing cold water so that you get good pressure throughout the house, plus a very well insulated tank with an immersion element for hot water. This is an older style, and was intended to compensate for low pressure inbound systems by having it all gravity fed, and isn’t really needed anymore since inbound pressure tends to be better since the introduction of more powerful centralised pumping stations.
Since the development of more efficient insulation and _much_ faster heating systems, a lot of properties now have combined boilers, which heat water to 55-80 degrees (depending on settings) as it flows through them. Modern ones are very good, and give you unlimited hot water- I have a 35kW boiler which can provide hot water to the kitchen and two showers at the same time. Between that and better pressure from the mains supply, the older style is becoming less common.
And yes, the tanks can be gross – many are more modern and enclosed plastic, but y’know, a big old rusty tank with a loose lid isn’t going to be _clean_…
Water for cold taps is drawn direct from the supply, where it doesn’t matter if there is some interruption to the supply hot water is stored in the attic in case of an interruption to the supply. Water can be fed to the hot water system with a continual supply, if you don’t have this when the water goes off and you heat all the remaining hot water and use it up the boiler then heats nothing and when the supply come on water is added in and immediately evaporates to steam and explodes the boiler.
Water tanks fill from the mains and provide pressure (“head”) to the rest of the system. They are generally cold-water.
The immersion heater is a giant kettle. You turn it on to heat it up, it heats the water and then it stays warm for a long time and that supplies your hot water. If you have an immersion tank, your hot water is probably just as clean as your incoming mains.
And depending on how it’s plumbed, yes, it could be that the cold water is fed from a tank in the attic, that should be covered and things shouldn’t be able to get into it. This is literally a “have a look, remove anything that shouldn’t be in there, and cover it” job, not a huge inconvenience or even a regular occurrence. Just keep it sealed to keep your water clean.
That said, both are on their way out – immersion heaters are being replaced by instant hot water heaters, water tanks aren’t necessary if you have pressurised hot water heaters, and power showers / boilers are taking over from any need to have to have a lot of water stored above your house or heat water for a shower.
Generally the system you describe is the 1960’s/1970’s system for powering a house entirely with electric. This is archaic, yes, but still present in many houses. And now that gas boilers will soon be banned, it actually works to your advantage and can be modernised quite easily.
<– Someone who bought a 1960’s house with this exact setup and intends to replace it all with a small instant boiler, a power shower, and solar power for whatever I can manage to do.
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