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This article was written by Larry Lunsford and appeared in the Mid Atlantic Koi Club Newsletter. If you are not in MAKC you should join now and be a part of one of the USA's largest and BEST clubs.

Introduction:

Many Koi keepers, especially the more Koi Kichi, have ponds that they want to heat. The simplest approach is to use electric heat. Electric heat is ok for small ponds or for temporary use, but the expense can get to be too much for larger ponds or for long term use. In many parts of the country, natural gas is significantly cheaper than electricity. This article will show you how to use your gas water heater to heat your Koi pond and save some money on your electric bill.

The figure shows the parts you need and how they connect into your water heater to provide heat for your Koi pond. The system circulates water from the water heater, to a heat exchanger, and back to the water heater. Water from the heater and water from the pond never mix -they just get close enough to transfer heat. The heat exchanger can be put in a variety of places. The figure shows the heat exchanger in its own tank as a separate stage in the filter. Pond water is pumped to the heat exchange tank, flows over the heat exchange coil, and then flows into the filter. The heat exchanger should be completely submerged and in an area where there is a good flow of pond water moving across it.

Calculating Heat Requirements:

Before going further, you need to determine how much heat you want your system to provide. Gas water heaters are usually rated in BTUs per hour. One BTU is the amount of heat required to raise the temperature of 1 pound of water by I degree Fahrenheit. Typical gas water heaters are rated in the range of 30,000 to 60,000 BTUs per hour. You'll have to decide how much of your water heater's capacity you want to divert to your pond.

If you are currently using electric heat, then it is an easy matter to calculate the BTUs you need. The formula for converting watts to BTU is:

BTUs (per hour) = watts x duty cycle x 3.4118 The duty cycle is the amount of time that your electric heater is on. Example: you have a 500 watt electric heater that is on 2/3 of the time. The BTUs is 500 x .666 x 3.41~8 1137.

Another way to estimate BTU requirement is to use heat loss per day. The formula is BTUs (per hour) gallons x degrees x 8.36 (pounds of water per gallon) I 24 (hours per day)

Example: your pond is 2000 gallons and you have a heat loss of 15 degrees per day. BTUs required is 2000 x 15 x 8.36 I 24 = 10,450 BTUs per hour.

Determining how much heat your pond will require is difficult because every one is different. Once you know your BTU requirement, you can calculate the water flow needed. The formula for water flow is:

flow (gallons per hour) = BTUs (per hour) I temperature drop in exchanger I 8.36

Temperature Drop:

The temperature drop in the heat exchanger is the difference between the water temperature when it goes into the heat exchanger and its temperature when it comes out. Most water heaters will put out water that is 110 to 140 degrees. The temperature of the water when it leaves the heat exchanger will be close to the temperature of the pond. Example: you calculated your BTU requirement to be 2000 BTUs per hour; your temperature drop in the heat exchanger is 50 degrees; flow = 2000 I 501 8.36 = 4.78 gallons per hour (GPH).

The flow rates calculated above assume that your system is constantly running. If your system only runs part time, then it will have pump proportionately more water when it is running.

Constructing Your System:

To build your heating system, you will need the following materials:

• Shutoff Valves (2)

• Circulating Pump

• Heat Exchanger

• Flow Regulating Valve

• Thermostat (optional)

• Timer (optional)

• Misc. Pipe and Fittings

The shutoff valves are used to isolate the system from the rest of the house water for servicing. The flow regulating valve is used to control the maximum flow rate of water through the system. This valve should be one of the multi-turn style so that you can precisely adjust the water flow. The heat exchanger is simply a length of pipe used to trade heat from the water from the heater to the water in the pond. You can buy a heat exchanger from companies such as Aquatic Eco Systems, or you can make your own. The heat exchanger should be made of something that can and water pressure of your water heater and is now . Suitable materials are stainless steel, titanium, plastic and aluminum. Cooper should be avoided since it is Koi and in some circumstances cooper could be dissolved into the pond water. Circulating pumps are available from plumbing supply stores. Select a pump that has adequate flow (you probably won