In many cases, the scale cannot be removed mechanically. The heat exchanger
may not be built for it, or the scale deposits may be too hard or thick. In these
cases, chemical descaling, using various types of acid is necessary. Information on
this process is in Section 5.2.5.
If the water being heated is potable (used for drinking, cooking or
bathing), the descaling solution should not be toxic! If this is not
possible, be sure to completely flush the heat exchanger with fresh
water after descaling.
While the system is running, check the temperatures at the inlets and outlets of all
heat exchangers. Make sure the temperatures change in the appropriate directions.
The fluid entering the heat exchanger from the collectors should be higher in
temperature than the fluid leaving the heat exchanger going back to the collectors.
The water coming in from the storage tank should be cooler than the water going
back to the tank.
If the heat exchanger has a sacrificial anode in the tube manifold, check it by
unthreading it, if it is accessible from outside the heat exchanger. If not, remove the
bonnet to check it.
If the anode is gone, or nearly gone, a replacement should be obtained and
If an exact replacement cannot be obtained, it may be possible to saw off a one or
two inch chunk of water heater anode and place it inside the shell. Use a standard
threaded plug to close up the port in the heat exchanger. Reinsulate the heat
Draindown Tank/Heat Exchanger
Add distilled or deionized water until the fill port overflows when the solar loop pump
Drainback systems are normally filled with distilled or deionized water.
6.1 MAINTENANCE PROCEDURES