If you have a solar pool heating system, your dealer may mention the manifold. This is just a set of valves that control the flow of water in your solar pool heating system. The function of the solar pool heat manifold is to turn you solar on or off by bypassing the solar panels when necessary. Your manifold may or may not include isolation valves to isolate the solar panels in the event that the system must be serviced.
Let’s take a look at an example manifold. The one pictured below includes two high quality Jandy brand isolation valves, a Jandy brand bypass valve, and a motorized actuator that is controlled by a pool automation system, in this case, an Aqualink system. Note that the bypass valve is also known as a diverter valve, a 3-way valve, or generically as a Jandy valve, which can be confusing.
Your solar pool heat manifold may look significantly different from this, but the concept is the same. We need to be able to control whether the water from the pool pump goes up to the solar panels, or bypasses the solar panels and returns directly to the pool. In the current configuration, the solar pool heating system is on, and water is able to flow through the panels on the roof. The red “X” is the bypass plumbing. When the bypass valve is in the other position, the solar panels are bypassed, and the water flows directly back to the pool.
The isolation valves should NEVER be closed when the bypass valve is in the solar-on position. This “dead-heads” the pump, meaning that the pump is running, but there is nowhere for the water to go.
It should be noted that the bypass valve is typically a “non-positive” valve. That means that it does not actually stop all of the water from going one way or the other. This is important so the water in the panels can drain back into the pool when the solar pool heating system is off. Draining water from the panels helps prevent freeze damage to the panels. This can be accomplished several ways, which are beyond the scope of this article, but note that it may not be readily apparent how your valve is made to be non-positive. Some systems, due to plumbing configurations, are manually draining. They must be drained manually or using a drain valve if installed.
Some common parts of the pool heating system plumbing are not shown here, like check valves that only allow water to flow in one direction. I’ll get to that concept in another article!
There are several ways to make a solar pool heat manifold, and some features may not be present in yours. If you have a question about your manifold, take a picture and email it to me at jason (at) facosolar.com and I can help you make sense of it!