Periodic Maintenance of your SHEM Simple Drainback Tank (and brackish water)

Periodic maintenance and checks are important for the health of your SHEM Simple Drainback or Simple Drainback With Electric Backup tank. The fluid level must be checked periodically to guard against leaks, or normal operation of the pressure and temperature valve. We recommend checking the solar fluid at minimum every 6 months.

When your system was installed, the solar fluid tank should have been filled completely. Then 2-3 gallons should have been drained off leaving around 2-4 inches of air in the tank. This allows for thermal expansion of the water in the tank so that the water doesn't expand and climb up the pipes to a non freeze protected section of the piping.

To prepare your tank for checking the fluid, make sure the pump has been deactivated for at least 3 hours. To ensure this happens unplug the pump from the SHEM32 Controller 2 hours prior to checking the fluid in the system. How your system was installed depends on how you check the fluid:

Preferred Method: If your system was installed with the included Blue-White flow meter at the top of the tank to serve as a sight glass, just wait for the level of the fluid to be seen in the sight glass, as seen in the example picture below. If your tank is low on solar water, use a hose, or a watering can to refill it to its normal level.




Alternative Method: If your system was not installed as described above, allow extra time for the tank to cool to below 100°F. Then release any pressure that has built up in the tank by actuating the T&P Valve. Once the pressure has been released, remove the T&P valve from the top of the tank using an adjustable wrench. Use a long and thin tool (such as a dowel rod) as a dipstick to check the level of the fluid. The fluid level of a near room temperature and completely drained back tank should be 2-4" below the top of the tank. If your tank is low on solar water, use a hose, or a watering can to refill it to its normal level.

Brackish Water: Over time you may notice the water inside your flow meter will turn a brown, black, or rust color. This is expected under normal operating conditions. The Wilo pump supplied with the system uses a cast iron impeller. Over time this cast iron impeller will naturally oxidize and corrode. Due to the design of the SHEM Simple Drainback system, this water is not introduced in any way to the hot potable water supplied by the system.

If this corrosion is unacceptable to the consumer, replacement pumps using impellers with alternate materials (bronze, stainless steel) can be purchased from Wilo and other pump manufacturers. Beware that these pumps are often priced much higher (often double the price) of the cast iron model supplied with the system.

SHEM does not recommend a system flush and fill as a regular maintenance item. Once the solar fluid has been turned brackish, further corrosion is retarded due to the depletion of oxygen in the water. Refilling the system with new water will only introduce new oxygen and provide opportunities for further corrosion.