Hot Tub Plumbing

Check Valves

The purpose of the check valve is to "check" the water flow to allow it to go only in one direction. The uses are many and will be noted in each equipment chapter where they are employed. However, three common uses are as follows:

• In hot tub heater plumbing, to keep hot water from flowing back into the hot tub filter.
• In hot tub air blower plumbing, to make sure air is blown into the pipe but water cannot flow back up the pipe and into the blower machinery.
• In front of the pump when it is located above the hot tub water level, to keep water from flowing back from the filter and into the hot tub when the pump is shut off.

There are two types of check valves. One is a flapper gate (also called a swing valve), and the other is a spring-loaded gate (also called a valve seat). The flapper style simply opens or closes with water flow. A diaphragm version allows water to pass on either side of a flexible membrane.

The spring-loaded style of check valve can be designed to respond to certain water pressure. Depending on the strength of the spring, it may require 1, 2, or more pounds (% to 1 millibar) of pressure before the spring-loaded gate opens. As with other valves, check valves are made of plastic in standard plumbing sizes and are plumbed in place with standard glue or threads.

The flapper-style valve is simple, and little can go wrong with it. It must be installed with the hinge of the flapper on top. If it were installed on the bottom, gravity would leave the flapper open all the time. The only real weakness of all check valves is that they clog easily with debris, remaining permanently open or permanently closed. Because of the extra parts inside a spring-loaded check valve, it is more prone to failure from any debris allowed in the line. If the valve is threaded or installed with unions, it is easy to remove it, clear the obstruction, and reinstall.

Another solution is to use the 90-degree spring-loaded check valve. This one allows you to unscrew the cap, remove the spring and gate, remove any obstruction, and reassemble. Be careful not to overtighten the caps—they crack easily on older models; newer models are made with beefier caps to prevent this problem. These units have an 0-ring in the cap to prevent leaks. It is wise to clean these out every few months (or more frequently, depending on how dirty the pool or hot tub normally gets) and lubricate the gate (using silicone lube only).

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