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Winterizing your Solar Pool Heating System
Winterizing your Solar Pool Heating System
Winterizing your Solar Pool Heating System

We get a lot of calls every year from customers wondering how to close down their solar pool heating system.  There are a couple rules of thumb to follow to make sure you have done a proper job.

The first thing to consider is when to do it.  Most important, of course, is to make sure you do it before the first frost.  We also recommend doing it after you have closed the pool.  You don’t want to close down your solar pool heating system only to have your pool maintenance company turn the pump back on and fill up the solar collectors again.  Your pool maintenance company or whoever closes the pool down will most likely blow out all the lines when they close your pool down.  But the question is, did they do a good job getting all of the pool water out of the solar pool collectors on the roof.

We also recommend putting the solar actuator into the ‘All Open’ position before you pool maintenance company blows out the pool lines.  That’s the position where the actuator has turned so that all the ports in the 3-Port valve are open.  The way to do this is to turn the switch on the controller whichever way you need to to get the actuator to rotate.  Once the valve moves into the middle position (see picture below – usually where the handle points to the pipe coming from the pool), unplug the controller.  This ensures that no water gets trapped next to the 3-port valve.

Solar pool heating system actuator in the middle position

The solar actuator in the middle position

If your roof is sloped, hopefully your solar installation company will have installed the system so that there aren’t any low points in the system that can trap water.  If there are low points, or if you have a flat roof, you will likely have to get on the roof and undo what we call end (or screw) caps.  In most cases these are just threaded caps that screw into the end of the panels at the bottom (see image below).

Solar pool heater end cap for drainage

Solar pool heater end cap for drainage

Usually the solar installation company has installed either screw caps onto a ‘T’ on both of the pipes going up to the roof or a couple of unions or ball valves with unions that can be unscrewed to drain the system out from the ground.  What we recommend our customers do is blow out both of these pipes from the ground with a Shop Vacuum, Leaf Blower or something equivalent.  Spend a few minutes blowing up each side until no more water comes out the other end.  If this is done and the pool is closed for the year, then you can be pretty certain that you have most of the water out of the system.  As long as no water is trapped in a low point, you can screw back in your unions or screw caps and leave it for the winter.   Again, in a flat roof situation it is a good idea to still go on the roof to unscrew the end caps to drain out the system.

Solar drain and shut off ball valve

For shutting off the solar pool heating system and closing down the pool

In the Spring, all you will need to do is plug in the controller, set the controller to AUTO and make sure the actuator is set back to the correct ‘ON’ position.   The actuator is the electronic box that sits on the 3-Port valve that automatically rotates it.  Remember sometimes the pool maintenance companies change the ON position on the actuator.  Actuators have a little toggle switch on the back that has 3 positions; ON1, OFF and ON2.  It’s a good idea to note which is the correct ON position for the actuator.  If the toggle switch is in the wrong position, then the solar actuator will rotate the opposite way that you want it to.

The way you determine if the actuator is in the correct position is simple.  Plug in the controller, set the controller to ‘Solar Test’ (or ‘Solar ON’ – see image below) and watch to see if the solar side (the side that goes up to the roof) is open.  You know it’s open when the handle points to the side that is the going up to the roof (See the image above).  The side that comes back down from the roof (commonly referred to as the Return) often has a one way valve (or check valve) on it and a ‘T’ that leads into the pipe that returns back to the pool.  If the handle is pointing in the direction of the Return, chances are the actuator is in the wrong ‘ON’ position and you need to switch it to the other ON position.

Solar controller switch Position

Solar Controller Switch Positions