Hot stuff

We talked on the blog a while ago about the way water enters your home and how it leaves. Continuing this occasional series, let’s take a look at what happens to the water while it is in your home – starting with the hot water system.

There are two types of hot water supply. 

All the hot taps may be supplied from a hot water storage cylinder that is fed from the cold water cistern and heated by a boiler or immersion heater.

Alternatively, hot taps may be supplied from a gas water heater or a cistern type electric heater connected to the rising main.  This is normally used when all the water is supplied directly from the rising main.

Water heating circuit

In a typical modern house with a central heating boiler there are two types of hot water circuit through the hot water tank – the primary circuit that heats the water and the secondary circuit that takes it to the hot water taps and radiators. 

The hot water heating circuit is supplied by a small feed and expansion cistern (usually situated in the roof space) that is supplied via the rising main.  A feed pipe goes from the expansion cistern to the hot water cylinder and then to the boiler.  When the boiler is heated the water in it expands as it gets hotter and becomes lighter than the cold water entering the boiler.  The hot water therefore rises out of the boiler along another pipe known as the flow pipe.  A branch of the flow pipe enters the boiler.  The rest of the pipe is left open ended over the expansion cistern to allow air bubbles to escape.

The part of the flow pipe that enters the boiler does not discharge water.  It continues through the boiler as a sealed coil which imparts heat to the cold water stored in the cylinder.

By the time this water has been through the cylinder it has cooled.  It joins the cold water feed from the expansion cistern and is returned to the boiler where the heating cycle begins again.  Hot water is constantly circulated while the boiler is heated.

Sounds complicated? Not really. But if you have a problem with your hot water supply it is best to call Drain Doctor rather than try DIY repairs – especially if they involve doing anything with gas or electric heating systems.



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