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hot water

Water heating is a heat transfer process that uses an energy source to heat water above its initial temperature. Typical domestic uses of hot water include cooking, cleaning, bathing, and space heating. In industry, hot water and water heated to steam have many uses.
Domestically, water is traditionally heated in vessels known as water heaters, kettles, cauldrons, pots, or coppers. These metal vessels that heat a batch of water do not produce a continual supply of heated water at a preset temperature. Rarely, hot water occurs naturally, usually from natural hot springs. The temperature varies with the consumption rate, becoming cooler as flow increases.
Appliances that provide a continual supply of hot water are called water heaters, hot water heaters, hot water tanks, boilers, heat exchangers, geysers (Southern Africa only), or calorifiers. These names depend on region, and whether they heat potable or non-potable water, are in domestic or industrial use, and their energy source. In domestic installations, potable water heated for uses other than space heating is also called domestic hot water (DHW).
Fossil fuels (natural gas, liquefied petroleum gas, oil), or solid fuels are commonly used for heating water. These may be consumed directly or may produce electricity that, in turn, heats water. Electricity to heat water may also come from any other electrical source, such as nuclear power or renewable energy. Alternative energy such as solar energy, heat pumps, hot water heat recycling, and geothermal heating can also heat water, often in combination with backup systems powered by fossil fuels or electricity.
Densely populated urban areas of some countries provide district heating of hot water. This is especially the case in Scandinavia, Finland and Poland. District heating systems supply energy for water heating and space heating from combined heat and power (CHP) plants, waste heat from industries, incinerators, geothermal heating, and central solar heating. Actual heating of tap water is performed in heat exchangers at the consumers' premises. Generally the consumer has no in-building backup system, due to the expected high availability of district heating systems.
Today in the United States, domestic hot water used in homes is most commonly heated with natural gas, electric resistance, or a heat pump. Electric heat pump water heaters are significantly more efficient than electric resistance water heaters, but also more expensive to purchase. Some energy utilities offer their customers funding to help offset the higher first cost of energy efficient water heaters.

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  1. B

    POTTERTON PROMAX 28 COMBI Boiler - Hot Water Issue

    Hello, I am seeking some advice, I have a POTTERTON PROMAX 28 COMBI Boiler and I noticed yesterday that the water around the house is no longer warming up. The heat exchanger has been changed 6 months ago, so I do not believe it is that. Does anyone have any ideas on what it could be? Thanks
  2. T

    No hot water flow

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  3. B

    Hot Water For Bathing Ideas

    I live in an apartment with a cold water tank. The cold water tank feeds the cold water tap in the sink and the bath. Recently, I refurbished my bathroom, and according to the plumber who fitted the new taps, high-pressure taps were fitted. Consequently, the water from taps is of a low volume...
  4. E

    Loss of Hot Water Pressure to Shower

    Looking for any ideas to help. I've a Heatrae Sadia Hot Water tank, heated through Oil fired boiler (working fine). A week ago I reset the air gap as I was having dripping from the pressure relief valve. Since then I've lost a lot of pressure from the hot water feed to my shower. The rest of...
  5. T

    Hot water flow/pressure

    I recently had an eco tec plus 836 combi installed as part of an oil to gas conversion. One thing I can’t work out is why the bathroom sink hot water flow is 12-13L per minute with at 44c and even hotter. However the nearby bath freestanding tap is 8-9L per minute at this temp. Both taps...
  6. P

    Milky hot water. Recently had a Viessmann 100-W combi boiler installed. Now when the hot water reaches any tap it is very 'milky'. This appears to be

    Milky hot water. Recently had a Viessmann 100-W combi boiler installed. Now when the hot water reaches any tap it is very 'milky'. This appears to be micro bubbles and clears, upwards, in a few seconds leaving no residue. Though this is a hard water area in 45 years have never had this cloudy...
  7. S

    No hot water in bathroom.

    The Water Board have just replaced the main water supply to our property. We have a ground floor combi boiler. The central heating system for the whole house is working as normal. Hot water is working as normal on the ground floor. However, there is no hot water to the first floor bathroom. This...
  8. K

    Problem with shower - old style electric hot water

    Hoping someone can please help. I have an intermittent fault with my electric hot water. I have an older style electric hot water service that heats on controlled load over night. The large tank is in roof space of 60s built villa unit. Every few mornings, no hot water will come out of...
  9. S

    Possible Leaking Gravity Fed Hot Water Cylinder Valve

    Hi all. This ‘valve’ is at the bottom of our domestic hot water cylinder. Anyone have any idea what it is please? It must’ve been there for many years and seems to be leaking.
  10. S

    Intermittent low hot water flow all taps

    Hello All, I wonder if you can help me? I have intermittent hot water low flow from all taps in my 4 bedroom house upstairs and downstairs. I can sometimes recover the usual water pressure by turning the hot and cold water taps on and off which seems very strange to me. There is no problem...
  11. S

    Drayton Digistat 2RF - Heating & Hot Water not working

    Heating and hot water is not working. Plenty of heating oil. I have replaced batteries in thermostat and it seems to be working ok, showing flame to call for heat, and the receiver seems to be working ok with green light, but heating is just not firing. I really am not sure what the problem is...
  12. M

    Bubbling hot water going to header tank

    Hi, I am looking for a bit of advice. Our Gledhill hot water tank was installed incorrectly 18 months ago and has been sending bubbling hot water to our plastic header tank in the loft every time we turned the heating on. We first noticed an issue with a leak in our bedroom ceiling which we...
  13. D

    OSO unvented hot water cylinder - Wi-Fi / programmable control

    Hi all, I have an OSO Direct 210 hit water cylinder installed in my home, with 2 switches (on/off; and boost). The boiler is for hot water only (rads are electric). In the 5 years that I’ve lived at this property, I’ve never once turned the boiler off; however, with soaring energy prices, I’m...
  14. G

    How to clear hot water air lock?

    I recently installed new hot and cold feeds to a new downstairs cloakroom. After refilling the system the hot taps were all dribbling, spluttering and showing signs of an air lock. I attached cold mains to a hot tap and left it running for 15 minutes, while opening up each hot tap. They all...
  15. R

    Limited Hot water in cold weather (Sorry posted twice)

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  16. R

    Limited Hot water in cold weather

    I have a 2 pump hot water tank (Flomax 180L fitted in '94) in airing cupboard system with an Ideal classic boiler (downstairs next to an external wall) which for the most part seems to provide excellent hot water. The central heating also works fine - though sometimes I think the radiuators...
  17. L

    Mains supply to mixer tap is pushing cold water to hot water pipe

    I live in an apartment block where generally hot water is supplied from the communal hot water cylinder and cold water to bathrooms is supplied from cold water tanks in the loft. It is a vented system. However, in a basement flat and a ground floor flat cold water supply to bathrooms is...
  18. R

    Bath/shower with no hot water

    Hello, We hade a problem with our hot water not working in one of our bathroom's (all other outlets were working) Therefore we got the Thermostatic Shower Valve changed and everything was working again. However a few days later, both hot and cold no longer works for the bath and the hot...
  19. I

    Underground hot water feed pipe.

    I've had a burst pipe under bathroom floor. Ive had it dug up and made safe with the affected pipe cut and end caps fitted. The pipes are cover with a plastic sheet and then screet on top. I called out my gas boiler cover to make a permanent repair. The company they sent out have said it is...
  20. B

    PLEASE HELP Hot Water Combi Boiler Advice

    PLUMBING ADVICE NEEDED Combi boiler in our house, downstairs water seems to be piping hot. Upstairs basin, bath and shower only ever seems to be lukewarm - so much so that no one even wants to bath as it never gets hot enough! Open to suggestions as to what it might be and if anyone can...
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