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Water source heat pumps: Everything you need to know

Water source heat pumps are an extremely efficient way of heating your home and providing you with hot water.
water-source heat pump

Water source heat pumps work by extracting heat from a body of water and turning this into energy that can be used to heat your home and supply you with hot water. As heat transfers better in water, homeowners typically find that they are more efficient than ground and air source pumps.

They are an ideal way to reduce the environmental footprint of your home, especially compared to traditional boilers that rely on fossil fuels such as gas to operate.

TYPES OF WATER-SOURCE HEAT PUMPS Closed or open loop system: know the difference.

Water source heat pumps come in two types: closed loop and open loop system. In general, the closed loop system is more common. The open loop system is only advisable in limited cases. Let's take a closer look at which system is more suitable for your home.

The optimal condition for a closed loop water source heat pump is a property with sufficient water nearby. In this system, the necessary pipes are laid underground and in the water. The advantage: due to the simple installation, this variation is more cost-effective than the open loop system.

Open loop systems require additional regulations for installation and use, as the system actively draws in water for operation (f.e. from a pond). The water must be clean and sufficient for the system to draw water from the main water source and filter it.

FUNCTIONALITY OF A WATER SOURCE HEAT PUMP How does a water source heat pump operate?

Water source heat pumps tap thermal energy stored in the groundwater by means of two wells: a suction well and a discharge well. With these, the heat pumps can heat and cool.

Operating principle of a water-source heat pump

From the suction well, a pump transports groundwater to an evaporator inside the heat pump. The evaporator passes the groundwater heat on to a liquid refrigerant, causing it to evaporate. This vapour is now compressed and heats up further until it becomes gaseous, and the contained heat is fed into the heat exchanger.

From here, the heat is either passed on directly to radiators or underfloor heating and the domestic water production, or to a buffer storage that supplies the heating system.

Functionality of a water-source heat pump

The water from which heat was extracted is then led out into the discharge well. The refrigerant passes the heat onto the heating system and re-liquifies. It then reaches the expansion valve that regulates pressure inside the heat pump unit. At the expansion valve, the refrigerant cools down until it can absorb groundwater heat again and the supply loop thus closes.

SUITABILITY CHECK Does a water heat pump suit my house?

Whether a water heat pump is suitable for your house depends on various factors.

  • Water quality

    The first thing to clarify is what the existing water quality is like - the water authority or a geologist can tell you about this.

  • Groundwater source

    The groundwater source should be at a maximum depth of 15 meters for lower construction costs and lower electricity consumption of the well pump.

  • Insulation

    Each property is unique, but it is important to understand what other measures can be done to reduce heat being lost in your home. Looking at loft insulation and whether you have double glazing windows is a good start. Consult a professional for further guidance on what is feasible for your home.

  • Individual factors

    Need more help? Simply contact your local Vaillant heat pump installer who will be able to help answer any questions about water source heat pump suitability for your home.

Since water-source heat pumps are only one variation of three, there are arguments for it and arguments for the other heat pump variants.

  • Pro: Sustainable

    Your house is heated in an environmentally friendly way by using thermal energy from groundwater.
  • Pro: Cost-saving

    Water heat pumps have low operating and maintenance costs.
  • Pro: Flexibility

    A water source heat pump provides heating, cooling and the comfort of hot water.
  • Pro: Space-saving

    Vaillant water heat pumps require only a small space in your home.
  • Con: Installation

    Compared to other heat pumps, the water heat pump has comparatively high initial costs due to intensive planning. The installation through two boreholes is time-consuming. But once the investment is completed, you will benefit from the advantages for many years.

Costs and financial support for water-source heat pump

The Boiler Upgrade Scheme (BUS) government grants helps homeowners in England and Wales with the cost of installing a low carbon heating technology in your home.

You can recieve up to £7,500 off the cost and installation of a ground source heat pump (includes water source).

To learn if you're eligible and how to apply for BUS, click here.

With two mandatory wells as part of the system, overall costs of water-source heat pumps are significantly higher than for ground-source and especially air-source models. Yet, about half of the expenses are due to the increased amount of development works like drillings, construction and installation of the heat pump.

Though, the higher initial costs pay off in relatively short time thanks to significant savings on running costs thanks to the high efficiency.

FIRST STEPS & PREPARATIONS Planning your water-source heat pump.

  • Know the area where you want to drill

    You’ll have to make sure that you don’t live in a water conservation area where operating a water-source heat pump is generally prohibited.

  • Obtain a permission for drilling

    The drillings depth is ideally at around 15 metres or less and crucial to the heat pump’s efficiency. The construction of wells with less depth is much cheaper, too. The ideal diameter for the well is determined by the amount of water that must be continuously available to ensure an adequate supply to your home.

  • Have a test drilling

    The first is a test drilling to analyse the concentration of oxygen and solids like manganese and iron in the groundwater – if results are too high, substances in the groundwater may cause deterioration of the heat pump.

  • Find the perfect place for your heat pump

    Your water-source heat pump should ideally be installed in your home's utility room. This also makes for a very space-saving solution, as the heat pump doesn’t require any more space than a regular refrigerator.

FAQs Common questions, clear answers.

  • What’s the average life expectancy of water-source heat pumps?

    Heat pumps usually have an average life span of 15 years, with some newer models lasting significantly longer (20-25 years).

  • How often does a water-source heat pump need maintenance?

    Since water-source heat pumps are hermetically sealed systems, they’re basically maintenance-free. Only the level and quality of the groundwater as well as the heat pump's filters should be checked on a year-to-year basis.

    Despite the relatively high robustness of the appliances, these intervals must be observed in order to maintain their warranty. Standard maintenance of a water-source heat pump is rather low-priced at around € 150.

  • How loud is a water-source heat pump?

    Water-source heat pumps usually create no or – if any – barely any audible operating noise when they’re intact and have been installed correctly.

  • Does water quality matter for water-source heat pumps?

    The groundwater should contain as little manganese and iron as possible. Both substances may cause damage to your system, primarily to the heat pump’s heat exchanger and the two wells. In most cases, the evaporator heat exchanger in the refrigerant circuit is protected from insufficient water quality by an additional heat exchanger.