How do I Build a Water Heated Wood Fireplace?

Written by natasha parks
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How do I Build a Water Heated Wood Fireplace?
Water heated wood fireplaces have comparatively low running costs. (Jupiterimages/Comstock/Getty Images)

To create a water heated wood fireplace, a heat exchanger set-up needs to be built that will connect and transfer energy between a wood stove and a water tank. The wood stove is vital in making an efficient water heated wood fireplace. The gases taken from a contained fire (as opposed to an open fire) will provide enough energy to heat the required volume of water in the tank resulting in heat to power your home's heating system or underfloor heating. These are both common requirements of a wood fired water heater.

Skill level:

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Things you need

  • Tape measure
  • Chisel
  • Mallet
  • Concrete
  • Iron or steel wood stove
  • Back boiler
  • Stainless steel connector pipe
  • Water tank
  • Rock wool
  • Stove putty
  • Radiator key
  • Large, plastic tub
  • Heat leak radiator
  • Central heating pipes
  • Corrosion inhibitor cartridge

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  1. 1

    Plan to install a functional wood stove if necessary. Measure the space between the proposed location of the wood stove and the internal walls of the fireplace using a tape measure. Plan to make room for a wood stove, a back boiler and connecting pipes between the two.

  2. 2

    Open the fireplace if more space is needed. Identify the curved, brick arch or the lintel (a horizontal length of concrete or steel supporting the upper chimney breast) by removing the plaster from the brickwork with a chisel and mallet. Work carefully to prevent damage to the underlying brick fascia, as it provides structural support. Remove the bricks below the builder's arch or crosspiece lintel.

  3. 3

    Ensure the hearth beneath the stove is secure, level and meets the building regulations required for wood burning stove installation outlined in approved document J. For example, according to Planning Portal, the hearth must be at least a 1/2-inch in thickness to support the stove's weight, and should be made from non-combustible material, such as concrete.

  4. 4

    Replace the old fixture with an enclosed iron or steel wood burning stove that conveys the correct amount of heat for the size of space that's required. Remember, if the intention is to heat more than one room of the house using the back boiler system and radiators, the stove may need to be more powerful to cope with the additional requirements.

  5. 5

    Fit a back boiler to the stove via a stainless steel connecting pipe. Select the rear attachment point on the back of the stove rather than the opening on the top of the stove (only recommended for stoves without back boilers). Ensure the connector fits neatly and precisely into the stove and also fits the boiler pipe. Secure them together and seal the joins with heat resistant stove putty.

  6. 6

    Fit a water tank in line with the back boiler of the stove to resolve the main issue with back boiler systems: it takes a long time to heat the large volume of water required to heat a house. Do not take hot water directly from the stove back boiler. Connect the back boiler to the water tank (stored in an adjoining room or cupboard) so the water can be heated slowly and the heat stored and distributed cost effectively. Insulate the boiler and storage facility with rock wool.

  7. 7

    Turn off the water at the mains. Drain the central heating system if the intention is to connect existing radiators to the new back boiler. Start from the lowest radiator in the house. Unlock the radiator valves using the radiator key. Allow the water inside the radiator to pour out into a large plastic tub. Wait until all the water has drained out of the system before continuing your installation.

  8. 8

    Plumb in a heat leak radiator "in series" (which means it is directly linked via pipework) from the back boiler, to act as a safety measure. Make sure the stove can offload any excess heat it produces to the heat leak radiator in the event of a back boiler pump failure or if the electricity switches off spontaneously. Connect the back boiler and radiators using 1-inch diameter central heating pipes, as advised by DIY Data. Heat leak radiators should be sized at 20 per cent of the stove's heat output to water, as explained by Stoves Online.

  9. 9

    Turn the water back on at the mains. Tighten the radiator valve using the radiator key. Refill the system slowly and carefully with new water by opening the top valve steadily. You should hear the water rushing into the radiators. Inject liquid corrosion inhibitor into the central heating system via the air bleed valve using a standard sized corrosion inhibitor cartridge to improve the longevity and reliability of the system overall.

Tips and warnings

  • Ask for your system to be evaluated by a professional before testing it, as by law, it must be approved by a qualified heating engineer.

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