Types of Drain back Solar Hot Water Systems

You require hot water on a daily basis for numerous things such as washing clothes, dishwashing and bathing. Choosing a solar water heater is not just good for nature but is also economical and caters to your family’s needs all year round. Solar hot water basically is water heated by using the power of the sun’s rays. You will find various types of solar water heaters in the market however; there are simply two main types that are prevalent in the market namely the pressurised glycol system and the drain back system. When hunting for a solar water heater you will always face the dilemma of choosing between the two.


The fundamental idea behind the working of a drain back solar water heater is very simple. When the temperature of the solar collector is 180 degree Fahrenheit higher than the tank, the pump turns on and water gets pumped through the collectors and heat exchange takes place. The heated water then goes down the sloping pipes and returns to the tank. Now the water is ready for use. As soon as this water gets consumed for various purposes, fresh cold water takes its place and the process begins again.

Type 1 Drain back solar hot water system

In this kind of system, there are two tanks, one for the solar storage and the second for the water heater. Both the tanks are of full size. It is suitable for a household of any size. The efficiency of this tank increases due to the fact that the heat exchanger is located on the load side and not between the tank and the collector unit.

Type 2 drain back solar hot water system

This type of system features a built in water heater with only a single pump attached to it. These systems do not actually function with a gas water heater due to the positioning of the flame. The in built water heater is not actually a winning point of this system because it wears out fairly quickly and is expensive. Another bad point about this system is that the solar efficiency of such a system decreases over time. Also, since the solar storage and the water heater are in the same tank, there is less space and hence less solar hot water can be processed.

Type 3 drain back solar hot water system

Unlike type two systems, type three system need two pumps to get the water heated. Also, the water heater in this system is placed in a small reservoir tank thus making it flexible to be fitted with any model of your choice. Both type two and three systems have the heat exchanger placed between the tank and the collector.

The best part of the drain back system is that at no point in time will the system come to a boil or freeze. Glycol based systems corrode the pipes over time where as drain back systems simply use water and hence your pipes can serve you longer. Solar hot water itself is a good conductor of heat and transfers up to 100% of the heat in the absence of a heat exchanger.

Need building inspections, Click Here