Every heating contractor moving into an empty boiler room ---- This room is usually the size of a small closet ---- must have his piping system outlined in his mind around the type of boiler and heat distribution system he will be installing. One of the main criteria for determining the plumbing configuration is the little check valve.

First, let's look at the three most common types of check valves:lift plunger, swing check, and spring-loaded check valves.

The Lift check valves in intermittent circulation systems are designed to prevent gravity circulation of the heat source when the circulator is in the off position.

The swing check valve allows water to flow in one direction only. It does not prevent gravity circulation. It is mainly used to prevent different circulator consumer circuits from interacting with each other and it eliminates the short circuit problem. Depending on the layout of the system, the water always tries to take the path of least resistance. The swing check valve allows the circulator to deliver water in only one way as the system is designed.

If, however, opposite forces of a second circulator are at times almost equal, pushing against the flow direction of the swing, annoying chattering of the valve will occur with the valve flapper being pushed back and forth rapidly by two opposing pump forces fighting each other.

Bothlift and swing check valves have two disadvantages: they are large and bulky, and can only be installed upright in horizontal piping.

For every flow check valve or spring check valve, a heating contractor needs in a system, he must provide a short horizontal pipe run. This almost always requires additional elbow fittings, increased labor, and use of valuable space.

One solution I have found to be very useful is the spring check valve. Every plumber who installs well systems is familiar with this clever little spring check that will make a heating contractor's day a lot better. It can be installed in any position. Horizontally, vertically, right side up, or upside down. It's very compact, with a 1-inch valve about 2 inches long. It is about half the price of a free check. It is non-ferrous and can be used for heating and plumbing.

It is available both as a directional rotary check valve and as a gravity flow check valve in sizes ranging from 3/8 inch to 3 inches. The spring check valve is particularly useful in installations where piping space is limited (which is not uncommon). The number of check valves required in a particular system can vary. Constant cycle systems essentially eliminate check valves to the point where only spring-loaded check valves are needed between the storage tank and boiler to prevent gravity circulation, and between the boiler and mixing valve to prevent short circuits through the 3-way or 4-way valve.

There is no need for a check valve on the heat distribution side of the mixing valve because the pump never shuts off and the mixing valve completely isolates the boiler from the radiation of the hydraulics during non-heat-demanding conditions. Intermittent cycle systems with multiple zone circulators require a gravity check for each zone. Spring checks have proven to be reliable and effective. Try using one on your next stressful job. They may be just the solution you've been looking for.