Homeowners Professionals

How long does water stay hot in a tank?

Your hot water tank is the place where all of your heated water is stored until you need to use it. Because of this, your tank should be good quality and made of materials that are effective insulators. A cheap tank may not keep your hot water warm for as long. In this article, we examine how long the water in your tank should stay hot for. We also offer further information about tanks, including what they’re made from and how you can turn your tank off.

How long will a hot water tank stay hot?

There are lots of factors that could determine how long your tank will keep the water hot for. Most hot water cylinder manufacturers suggest that the water will lose between 1 kWh and 2.5 kWh of heat per day. It is hard to give a specific temperature loss, or to say how long the water will remain hot for. The kWh unit stands for kilowatt hours and demonstrates how much power it took to heat the water up. The better insulated your tank is, the more efficient it will be, losing less heat and therefore using less energy to maintain the water at a set temperature without the need for reheating. Previously, hot water tanks weren’t supplied with any insulation, however regulations now state that insulation must be included with the tank when you purchase one.

As an estimate, the water in your tank should stay hot for a day or two. The larger the tank, the greater the heat loss will be, and it depends on the quality of your tank as well as the form of insulation you have.

If your tank is situated in a cupboard, you might be able to determine how much heat your tank is losing based on how warm the cupboard is. An airing cupboard should be a little bit warm, but if it’s over 30°C, your tank might be losing too much heat. You could invest in an insulating jacket for your tank. If you already have one, you could insulate the pipes by wrapping blankets around them. You could also apply an extra blanket to your tank. A well-insulated tank will keep your water warm for much longer.

What are hot water tanks made of?

Most  hot water tanks  are made of either carbon steel, stainless steel or copper. Copper is a very expensive metal, which has led to stainless steel being used as a cheaper alternative. In the interest of efficiency, a debate was started about how efficient stainless steel actually is and whether all tanks should instead be made of copper.

There are, however, plenty of benefits associated with stainless steel tanks. One of the main advantages is the reduced risk of corrosion. Stainless steel is slightly more hard-wearing than copper and may keep the water tank free from debris for longer. It is also stronger, particularly in comparison to copper, and therefore the tank does not need to be as thick. Finally, stainless steel is able to withstand high pressures, more so than copper. This is particularly beneficial in the case of unvented hot water cylinders. An unvented cylinder is connected directly to the mains, so a cold water tank isn’t required. This system works under more pressure than a  vented system, making stainless steel a suitable material.

Copper has its benefits too. It’s naturally antiseptic in small quantities (large quantities can be poisonous) so, although you won’t be drinking your hot water, the water is purified. Copper is recyclable too, so when you’re replacing your old copper tank, you could get some money back for weighing it in. It’ll be melted down and turned into something else.  

How to drain a hot water cylinder tank

Over time, it’s likely that your hot water tank will gather sediment and dirt from your heating system. It may need to be cleaned to keep it running efficiently. Before it can be cleaned, the tank will need to be emptied.

First, you must turn off the immersion heater, located on the tank, and the boiler. Then, you need to isolate the cylinder from its supply of water. You can do this by closing the gate valve which is situated on the cold feed pipe. Turn the valve clockwise to close it.

Once you think your cylinder is isolated, you should turn your hot tap on until no more water comes out. This could take around 20 minutes.

Now that your cylinder is empty of hot water, you need to locate the draincock at the bottom of the tank. It could be on the cylinder itself or near the cold feed. You should place an old towel underneath the draincock to catch any water that could come out.

Next, attach a hose to the draincock using a jubilee clip and run the hose to the nearest drain. This could be a sink, bath or shower drain.

Finally, open the draincock using a key or a pair of small adjustable grips. Water should start to flow. Wait until the flow stops completely, and your tank is now empty. 

How to turn off a hot water tank

If you think you have a problem with your hot water tank, you can turn it off completely until a suitably qualified heating engineer is able to take a look at it.

There are numerous ways to turn off your hot water tank. You could shut off the gas, electricity or water supply. Turn off the gas by twisting the dial on top of the thermostat to Off. Turn the electricity off by flipping the circuit breaker to the Off position. To switch off the water supply, twist the handle on the water valve in a clockwise direction until you can hear the water stop. 

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