Hot water storage tank

Two red paralleled hot water storage tanks connected to a wood-fuelled furnace.
A hot water storage tank where one of the heat sources is solar heating A, that is sent into the hot water storage tank via a smaller pump B (circle with triangle) and the heat exchanger spiral in the hot water storage tank. The other spiral C can be used for a e.g. oil-fired boiler or a wood burner. At D the hot water gets out and domestic cold water is sent back at the bottom at E.
A hot water storage tank where one of the heat sources is solar heating. Almost the same example as above, but in a domestic habitat.

A hot water storage tank (also called a hot water tank, thermal storage tank, hot water thermal storage unit, heat storage tank, hot water cylinder and geyser in South African English[1]) is a water tank used for storing hot water for space heating or domestic use.

Water is a convenient heat storage medium because it has a high specific heat capacity. This means, compared to other substances, it can store more heat per unit of weight. Water is non-toxic and low cost.

An efficiently insulated tank can retain stored heat for days, reducing fuel costs.[2] Hot water tanks may have a built-in gas or oil burner system, electric immersion heaters. Some types use an external heat exchanger such as a central heating system, or heated water from another energy source. The most typical, in the domestic context, is a fossil-fuel burner, electric immersion elements, or a district heating scheme.[3]

Water heaters for washing, bathing, or laundry have thermostat controls to regulate the temperature, in the range of 40 to 60 °C (104 to 140 °F), and are connected to the domestic cold water supply.

Where the local water supply has a high content of dissolved minerals such as limestone, heating the water causes the minerals to precipitate in the tank (scaling). A tank may develop leaks due to corrosion after only a few years, a problem exacerbated by dissolved oxygen in the water which accelerates corrosion of both tank and fittings.

  1. ^ "geyser - definition of geyser in A Dictionary of South African English - DSAE". dsae.co.za. Retrieved 2023-03-05.
  2. ^ Cite error: The named reference sysdhw was invoked but never defined (see the help page).
  3. ^ "District Heating from Wind: Kirkwall". University of Strathclyde Engineering. Retrieved 20 January 2016.