From the United States of America? - Checkout our specific plumbing forum for you:USA Plumbing Forum

hot water

Water heating is a thermodynamic 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, 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 and Finland. District heating systems supply energy for water heating and space heating from waste heat from industries, power plants, 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.

View More On
  1. M

    Getting hot water when central heating is on

    Hi, hot water is switched off however when central heating is switched on, there is hot water too, can anyone tell me why this is happening g
  2. T

    Vaillant diverter valve works but not when hot water cylinder is refilled and tap open...

    Hello, I am not going to make any repairs myself on my boilers but no plumbers have been able to solve my issue. I am seeking for help on this forum to find the cause of the issue I face so that I could communicate to the plumber. I tried on french forums since I am from France but I have not...
  3. T

    False call for hot water

    Good day I’ve had three heating engineers look at the symptoms that follow to no avail. One of them replaced the electrodes ( part 5110992 ) Boiler: Potterton Promax HE Plus (SL) (2008) Hot water tank: Heatrae Sadia Megatech Solar 190 Indirect (2008) Thermostat: Nest 3rd Gen (2017) Symptoms...
  4. R

    intermittent hot water bathroom?

    I have an old vaillant combi gas boiler, turbomax. woke up this morning to find the upstairs doesn't get hot water, out of the hot water tap comes cold water. the pressure is normal it's just cold. however the hot water is intermittent, I find that after a while hot water does come out...
  5. RockyLeeLee

    Advice re adequate hot water for master bathroom in Loft Conversion

    Hello, and thanks in advance for reading my essay! I'm hoping to get some unbiased advice on the best way forward. I'm currently going through a permitted development application for a dormer loft conversion which will create a large master bathroom which will have both a whirlpool bath and a...
  6. K

    Hot water venting into header tank, this issue not covered on previous posts

    Hi all, I'm new to this forum, I apologise if I miss any protocols My issue on the face of it has been covered many times, but specifically in this instance it makes no sense and I have not yet found a reasonable answer, if you can help it would be very much appreciated. I have an open vented...
  7. S

    Hibernation of a hot water system with solar water heater

    Hello, I would like to have the opinion of professionals. My family owns a house in a village in Greece, where temperatures do not fall below 5-10 degrees Celsius in winter. The house is located in a location where the water supply is not constant and with low pressure (which justifies the...
  8. D

    URGENT want to fit tmv2 but supples to basin taps not balanced pressures

    have gravity hot, mains cold to basin taps,require to fit a tmv2 anything i can fit to avoid trying to get gravity cold to taps to balance
  9. M

    Could water be convecting from the hot water tank?

    I have a sealed heating system with a Flowmaster Titan Plastech tank in the garage. The hot water pipe exiting from the top of the tank is hot to touch all the way up until it enters the house even when hot water is not being drawn. The pipe has a horizontal dog-leg before it is routed...
  10. M

    Turned off wrong valve, now hot water won't work in basement

    New homeowner. I was trying to prep for winter by draining the outside hose. I thought I found the right valve, turned it off and ran the water outside. The water didn't stop flowing so I figured it was the wrong valve. Went back inside to find that the shower head in my basement washroom was...
  11. H

    Kerosene Boiler Worcester 12/18 Heatslave "hot water expansion" !

    This heating system is new to me, in reality about 8 years old and in good condition. In the tail end of last winter's heating season, I think I shot myself in the foot. With more bedrooms than occupants and a water cost of about £4/tonne, I had a water meter installed. It might have been a...
  12. I

    No hot water - boiler showing no error code

    I have an 18mth old ecoTec plus 825 Vaillant boiler. We have had intermittent problems with the hot water supply for the last 2 days - now there is no hot water whatsoever, although the boiler is showing no error code. When you run a hot tap - there is not the little flashing tap sign on the...
  13. L

    URGENT No hot water - help needed

    Hi everybody I live on my own and my parents are away so in desperate need of some help!! I have a Vaillant Eco Tec Pro boiler. On return from holiday a few days ago, my heating wouldn’t come on and the hot water was luke warm. I noticed the water pressure had dropped to nil and the thermostat...
  14. I

    Dripping Tundish on a Tribune HE hot water tank

    Tundish dripping, not sure if TRV or another pressure relief valve, the mini white tank not being upto pressure or something else. Suppose job will be work out problem of dripping, and also help identify why diverter valve won't activate when hot water is needed to be tested. I have to hit the...
  15. I

    2 port sunvic diverter valve not activating

    I have a sunvic 2 port diverter valve on a tribune HE hot water tank, it's not activating when hot water needs heating. I've replaced the thermostat, but have to hit the diverter valve a few times to get it to activate. Any idea what may be causing the motor to stick as it is working just needs...
  16. J

    Tankless oil boiler/water heater - not enough

    We are a family of 5, we are not getting enough hot water from our relatively new tankless heater (it fluctuates in heat all the Time and won’t fill up a bath consistently with hot water - can’t support 5 people) . We want to add a water tank to increase amount of hot water available but have...
  17. C

    Managed to boil my hot water tank with immersion heater...

    Woke up at 6AM to the sound of my hot water tank boiling and a cold sweat as I realised I'd left the immersion on since 6PM the night before. Immediately turned it off and opened the taps in the bath to drain the tank, temporarily turning my bathroom into a steam shower - still not sure if this...
  18. K

    Running out of hot water after 3 minutes

    I’ve had a new bathroom put in and having problems with the shower. The pressure is awful and runs cold after about 3-4 minutes. The hot water still comes out of the taps and we have another shower which has never run out of hot water after 15/20 minutes plus and is still working perfectly. The...
  19. S

    VENTED central heating system - water circulating through header tank

    Two years ago, I requested a fully qualified plumber to change the location of the hot water cylinder in a vented central heating system. I wanted to move it from the first floor to the loft, which he did. During the last two years, I have often noticed when I have been up in the loft that the...
  20. M

    Hot water not working

    Hi. My Potterton Suprima boiler stopped working- red light on constantly. I replaced the PCB with a new one. Then the boiler worked fine but no hot water. Heating working normally. S plan system. The water would only work if I put the 2 port valve on manually. So I changed the actuator - Danfoss...