Koi Pond Heating Guide

Heat pumps are an excellent way of heating koi ponds through the winter and summer months.

Using a heat pump as a pond heater will significantly reduce your pond heating costs compare with all other forms of pond heating.

Below is a guide to the costs to heat a koi pond using different heating methods. This is an average/guide as the cost of heating a pond will vary according to the time of year and the weather, however this still provides a useful illustration of the savings that using a heat pump can bring.

Maintaining a reasonable pond temperature throughout the winter and spring (eg +12c) can have significant health benefits for the fish, helping to prevent disease and parasite attack

For use with koi ponds, it is important to select a heat pump that can operate down to low temperatures in order to maintain the required temperature of the pond throughout the winter and spring.

Typically a koi pond will be kept at between 10c and 15c throughout the winter and around 20- 22c in the summer.

The range of heat pumps that we recommend for koi ponds are the excellent Thermotec Inverter Pond Heat Pumps or the Duratech Dura+ range. The Duratech Dura+ range come in different sizes of 7kw, 10kw, 14kw, 19kw, 22kw and 30kw of output heat. Beware of other heat pumps that will only work down to about +7c, as these will become inefficient in very cold weather.

Our Duratech Dura+ and Thermotec Inverter heat pumps provide the highest output at lower air temperatures compared with other heat pumps on the market.

Thermotec Inverter 17kw on koi pond

Whilst there are cheaper heat pumps available on the market, the slight extra cost of the Duratech Dura+ and Thermotec Inverter ranges are worth it in terms of performance, reliability and suitability for use on koi ponds.

A heat pump can be used all year round to provide a stable pond water temperature. A stable water temperature provides siginiicant health benefits for the fish.

Our Thermotec Inverter and Duratech Dura+ ranges can operate down to –15c and have a “hot-gas” defrosting mechanism which will quickly clear away any ice that may form on the heat pump at low temperatures.

Thermotec Inverter 12kw heat pump on koi pond

Dura+ heat pump on koi pond

1. Sizing

For a koi pond that is heated all year round with a winter temperature of around 12c and a summer temperature of around 20-22c, we recommend the following sizing:-

(Note: This assumes that the pond is covered in winter and that a temperature of +12c is to be maintained over winter)

A cover should always be used on the pond in winter to help retain the heat and reduce heat loss (see below for our range of pond winter covers). In addition, any insulation that can be built into the pond walls and floor will be beneficial in reducing heat loss and hence reduce running costs.

Thermotec Inverter 12kw on koi pond

2. Efficiency

Heating a koi pond with a heat pump will always be significantly cheaper than using gas, oil or direct electric heating.

Our Duratech Dura+ heat pumps will return between 2.8 and 6.7 times their input energy as heat depending on the air temperature.

The Thermotec Inverter models can output up to 13 times their input energy as heat

This factor of efficiency is called the COP (Coefficient of Performance) and you can view a graph of how the unit performance varies with air temperature on the Dura+ product page Here

At an air temperature of 0c and water temp of 13c, the Duratech Dura+ heat pumps have a COP of about 4.

ie even at 0c air temperature, they will still output four times their power input as heat. The COP rises to over 6 as the air temperature rises.

This performance exceeds virtually all other heat pumps on the market. The output of other heat pumps will fall to virtually nothing as the air temperature falls. Many other makes of heat pumps that claim to be suitable for koi ponds are in reality only for summer use.

The Duratech Dura+7 has an input power of 1.2kw and therefore with an air temperature of 0c, it will still output 4 x 1.2 = 4.8kw of heat for only 1.2kw of input power.

The COP rises to over 6 meaning that the heat pump can produce 6 x 1.2 = 7.2kw of heat from only 1.2kw of input power.

These heat pumps therefore have an efficiency of between 280% and 670%. A typical gas boiler will only be around 85% efficient and direct electric heating is about 95% efficient.

This high efficiency makes heat pumps the cheapest form of heating for koi ponds, even at low air temperatures.

3. Controls

The Thermotec Inverter and Duratech Dura+ heat pumps can be set to keep the water temperature between +7c and +40c and the temperature can be increased in 0.5c increments.

Note that some other heat pumps on the market have a minimum set temperature of +15c which is too warm for most koi ponds in winter. Most koi ponds are kept at around +12c in winter.

The ability to set the desired water temperature to within 0.5c accuracy is another important feature of the Duratech Dura+ units. The temperature of most other heat pumps can only be changed in 1 degree increments.

The controls on the Duratech Dura+ range therefore allow you to have precise control over the pond water temperature.

Thermotec Inverter 17kw on koi pond in winter

4. Heating and Cooling Capability

The Thermotec Inverter and Duratech Dura+ ranges of heat pumps can heat and cool the pond water.

In summer, if the pond temperature exceeds the desired temperature set on the heat pump (eg 20-22c), the heat pump will then automatically enter cooling mode to reduce the pond temperature.

The accuracy of the controls on the Duratech Dura+ range helps to prevent temperature fluctuations to the pond water temperature to provide a stable water temperature.

5. Fish Health Benefits

Maintaining your pond at a stable temperature will have significant health benefits for your fish.

Keeping the pond at a reasonable and stable temperature (eg 12c) during the winter and spring months will keep the immune system of the fish active.

This can reduce the risk of the fish contracting diseases and being attacked by parasites, particularly in the Spring.

6. Running Costs

As an example of running costs, the Dura+ 7kw heat pump has an input power of 1.2kw (5.2 amps).

If your electricity costs say 9p per kwh then the running costs of the heat pump would be 9 x 1.2 = 10.8p per hour while the heat pump is operating

Except in extremely cold spells, and if sized correctly, the heat pump should not need to run 24hrs a day.

The heat pump will heat the pond to the required temperature and will then switch off.

The running time of the unit will depend on the air temperature and how well the pond is insulated or covered.

Assuming the heat pump needs to run for say 7hrs per day, the running cost for a Dura+ 7 unit would be 7 x 10.8p = 75.6p per day

7. Warranty

The use of the Thermotec Inverter and Duratech Dura+ ranges of heat pumps on koi ponds does not invalidate the warranty in any way.

The only provision in the warranty document states that for koi ponds, the PH must be kept between 7.0 and 8.5 which is fairly typical for most koi ponds.

The concentration of medicinal chemicals that may be used in koi ponds is not sufficient to cause any damage to the unit.

The Dura+ units have a titanium heat exchanger which is highly resistant to corrosion from all chemical types including chlorine in swimming pools.

A copy of the warranty document is listed at the bottom of the Dura+ product listing, or can be viewed Here

8. Customer Videos

Please see below some customer videos from Wrighty of using a Thermotec Inverter heat pump to heat his koi pond. Many thanks Wrighty !

9. Further Advice for Installing Heat Pumps on Koi Ponds

• A backup heat source (eg electric heater) should be installed alongside the heat pump. This can provide additional heat in extremely cold weather conditions (eg below -5c) and also acts as a backup in the unlikely event that the heat pump fails.
• In order to prevent damage to the heat pump, you must avoid water freezing inside the unit as this can crack the heat exchanger. The easiest way to avoid this is to keep the water circulation pump running when the air temperature falls below 0c.
• A frost stat can be installed on the circulation pump to turn it on when the air temp falls below 0c.
• The heat pump contains a pressure switch which detects when the circulation pump is running and water is flowing through the unit. In order for the pressure switch to work properly, it is advisable to install the heat pump on a pressurised water pipe as opposed to a gravity fed one. If the heat pump must be installed on a gravity fed water pipe, then we sell a separate water flow switch which can be used to detect water flow. Please Contact Us for details.
• The Duratech Dura+7 require a flow rate of around 3 m3/hr (660 gallons per hour) to operate effectively.
• A separate drip tray heating kit is now available which will melt any ice which builds up in the bottom of the heat pump. Please Click Here for details
• Please also refer to the Installation Tips on our web site
• Note that some heat pumps (eg Thermotec Inverter) require a minimum water temperature of +8c and above in order for the heat pump to start. If the initial pond water temperature is below this, then it may be necessary to use another heat source to raise the pond temperature above +8c so that the heat pump can then take over the pond heating.

10. Drip Tray Heating Kit

In extremely cold weather, the condendsation that drips from the heat pump evaporator coil can freeze in the bottom of the heat pump causing an ice build up.

We sell an optional kit that contains a special  heating wire controlled by a low temperature thermostat.

The heating element only turns on when the air temperature falls below zero and turns off again when the temperature rises.

The kit comes with all necessary parts and full installation instructions

Click Here to Purchase this Kit

11. Example Installations

Below are some photographs of a heat pond being heated through the winter using a Duratech Dura+ heat pump.

Another example below of a Duratech Dura+ heat pump heating a koi pond taken March 2010

The pond owner reported that the heat pump has worked extremely well and maintained the pond temperature at 15c despite the snow !

The running costs were reduced by approx 60%

Another recent installation was on a 14,000 gallon pond in Norfolk and used a Duratech Dura+14kw unit to heat the pool.

The pool owner reported:-

“I am writing to say I have been very impressed with the heat pump, I reckon over the past 3 weeks it has already saved me over £200 in heating oil”

The initial purchase cost of a heat pump may be higher than a traditional electric or gas pond heater, but you will soon recover the outlay through greatly reduced running costs.

Using a heat pump to heat your pond is also a more environmentally friendly method than using fossil fuels such as gas or oil and so you can also reduce CO2 emissions and do your bit for the environment !

12. What our customers say

Here are some quotes from our customers that are using Duratech Dura+ heat pumps on their koi ponds:-

On the example below the pipes from the pond to the heat pump were run underground in flexible pipe

Bypass kit and solid to flexible pipe connection shown