• Welcome to PlumbersForums.net - The international free plumbing advice forum. Professional plumbers sharing advice with fellow plumbers and DIY alike. Register for free today! - Checkout the Plumbing Advice forum and then our Plumbing Videos area which still needs populating.

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.

View More On Wikipedia.org
  1. K

    Worcester Bosch boiler not working for hot water

    My Worcester Bosch boiler works for the central heating system but doesn’t turn on for hot water. On the boiler the chimney sweeper icon is flashing and then 100. Not sure what this means or what I need to do? Can anyone advise as I’m clueless
  2. M

    Please help - thundering noise when I open the hot water tap

    Hello I have no experience in this industry. A few years ago our home was completely stripped apart, remodelled and extended. This required new hot and cold water pipes all over the house, a larger boiler, larger tank and so on - see attached. We wanted the water tank to go into the loft but...
  3. P

    Intermittent Hot water issue with Worcester Bosch Greenstar 35 CDI

    I have a 16 year-old Worcester Bosch Greenstar 35 CDi combi boiler, which is recently suffering from intermittent issues with the hot water. I usually get the shout from a family member who’s in the shower and found there’s no hot water. If I’m near the boiler when this happens, I can see the...
  4. K

    Hot water air lock after fitting new shower pump??

    Hi, I've just changed a stuart turner pump for a newer version (like for like). Cold water pressure is as should but hot water is trickling through maybe 35% of cold water pressure. I've turned pump off ran cold water for 5 min then hot water for 5 Min with shower head off to no joy any ideas...
  5. J

    Low hot water pressure

    I've had a new Firebird combi oil boiler fitted and the hot water pressure is low( in fact it's terrible)..the cold water pressure is good and I can't find any leaks and loose no pressure. Please help. Thanks alot
  6. Learning Plumber

    Hot water system plan

    Any experienced plumbers out there kind enough to take a look at my hot water system drawing? You can be critical - I'm learning! It’s designed to supply PV solar preheated water to an electric water heater and then on to small bathroom (daily light use). At the end of an ‘average' day, I...
  7. D

    Evohome firing boiler even when both heating and hot water set to OFF

    We have an evohome system, that controls both hot water and heating Heating is linked to two zone valves, and the full 12 allowed zones Switch heating to off, and hot water to off too Check smart meter at the end of the day and see 70p+ has been used on Gas (not standing charge, just usage -...
  8. J

    Heat and hot water suggestions

    Need suggestion for heat and hot water. New 1300 sf,2 bed 2 bath, 2nd home that will have daily and weekly renters.
  9. M

    Honeywell ST9400C - Have to put HW & CH on to get hot water

    May parents have a Honeywell ST9400C, when they want to heat up the emersion heater they have to switch the HW & CH on to get hot water. With the CH on as the same time the house gets very hot, just to have a shower! CAn any one advise what can be wrong?
  10. T

    Heat leaking out of hot water tank?

    Hi everyone Would love some advice! We have a hot water cylinder which lost 14 degrees (48 to 34) in four hours, with no demand/usage. So I think the heat is escaping. The circulation pump (which you can see in the photo) is off, so could passive convection be the reason? The pump is always...
  11. R

    Seitching to Combi boiler. Advice on hot water

    Hi everyone. I'm in the process of deciding if to switch from a traditional boiler to combi. One thing that is irrationally worrying me is if kids leave hot water taps running. Would that mean the boiler (if it was 30kwh boiler) would be running full pelt and using 30kwh gas every hour? Want...
  12. Tomjr98

    Range tribune HE no hot water??

    Ok guys so my Range Tribune He immersion heater stopped giving hot water a couple days ago (I’m a joiner with a limited knowledge in plumbing) also the hot water capacity was never that much it would do 2 showers a day. Any ideas of what’s up with it?
  13. S

    S Plan heating system, heating coming on with hot water

    Hi Guys, Had a question about a S plan system. When customer turns on a hot water tap the boiler gets demand for heating as well and radiators heat up, the heating radiator sign (Vaillant Boiler) flashes on the boiler display screen. Customer has said it has been like this for a year. I have...
  14. G

    Pressure drop not enough to fire dhw combi

    Currently have 14Mx15mm run from combi to tap dhw. If I replaced the last 6M section with 22mm pipe would this help? Taps closer to boiler have no problems firing the boiler.
  15. F

    Disconnect hot water

    Hi, I need to disconnect the hot water to the kitchen tap to repair a leak but there is nothing under the sink. We have a tank upstairs: Also, I followed this video but after loosening the screw with an Allen key, the handle will still not come off. I managed to stop the cold water. Any advice...
  16. J

    Why hot water copper pipe is 22mm and cold is 15mm?

    Hi All, I have this silly question. Water pressure for hot water is a bit low while cold water has a decent pressure. Why do they put 22mm copper pipes for hot water? It seems detrimental for already low pressure. Best regards
  17. O

    Logic 24 - hot water only turns on radiators

    When I turn on water only on the logic 24 boiler the water heats up and so does the radiators. It’s a a single floor apartment with the boiler recently serviced and the safety valve and 12 litre vessel change. Using the hive heating system.
  18. D

    What Causes A Hot Water Tank To Deteriorate?

    What are the factors that determine the life of a water tank? Obviously the quality of the water and the materials used to construct the tank are important. But beyond that I'm fuzzy. Is it just the number of gallons of water that pass through it? The number of "fresh" gallons of water that...
  19. P

    Boilermate 2000 No Hot Water / Past owner issue advice please

    Hi all, Just looking for some advice if anyone has worked on a boilermate 2000 try to condense the story, Lived in our home 3 years with the system working fine, but 2 days ago hot water stopped. From research it now looks like the past owner already had a problem. They have changed the...
  20. M

    Humming noise when hot water tap is on.

    When I turn on my hot water taps anywhere in the house, after about half a minute there is a humming noise all around the house. When I turn on the cold tap, the noise stops. Any ideas what is causing this humming noise?? Thanks Michael.