During the heating season, when your gas or oil fired hot water furnace is running, you might be surprised to find a wet floor starting right below a long copper pipe towards the back of your system. This pipe is connected to what is called a blow off valve which is designed to relieve pressure by allowing excess water to “blow off” or get expelled systematically.
There are three components that usually lead to this problem, and for more years than I care to remember I always recommend replacing them all at the same time.

First is the blow off valve itself, which will look something like this:

Muccia Plumbing & HVAC in NJEssentially, it is factory set to a specific pressure to match your furnace, and when that pressure is exceeded, it allows the excess water to be relieved through a vertically attached copper pipe (hopefully into a bucket that you should always keep just to minimize the need for mopping the floor). Note that the silver clip on top is simply a quick test to ensure excess water will flow if necessary.


Second is the feeder valve, which will resemble this part:

Muccia Plumbing & HVAC in NJThe feeder valve, as the name suggests, keeps a constant level of water in a boiler system and will over time require a replacement. Contaminants and other water pollutants will cause the feeder to fail. Failure may mean too much or too little water added, so it’s a maintenance part which should be replaced anytime there is a concern of water pressure imbalance in the system

Last, but not least, is the expansion tank, a 30-gallon model will often look like this:

TankAs water is heated in a boiler, it expands, and that expansion, if not controlled could cause pumps, pipes and other components to burst. It also helps maintain relative pressure throughout the system. When the system is initially filled with cold water, the pressure is equal to that in the pre-charged expansion tank. Inside the tank there is an air cushion diaphragm which is held flush against the tank. The added pressure as the water is heated is held by the expansion tank, and as the water cools, it allows the rubber diaphragm to return to its starting position.
WARNING: These tanks are usually filled at least part way with water even when the system is off. That makes them extremely heavy and quite dangerous for the do-it-yourselfer. Likewise, installation of a new tank, even though it is empty, is an arduous task since they are heavy, odd shaped, and tough to get the threads started by a novice.

So there you go! You now know more about hot water boilers than probably 90% of your friends and neighbors. While this is great should the topic come up at a cocktail party, we strongly recommend you leave this one to the pros.

Muccia Plumbing has literally replaced HUNDREDS of these important parts, and saved many Bergen County families. We’ve helped them avoid spending needless time and effort, buying the wrong parts, and cross threading parts during reassembly. In particular, water feeders are “sweat fitted” (soldered together using a plumber’s torch and training). Believe me, that is nothing to mess with when your floor is soaked and your house is cold; so call a professional plumber.

Just call us anytime of the day or night, our telephone operators are standing by, and our techs are on call 24 X 7 X 365.Muccia Plumbing & HVAC in NJ

Hey, I get it. It’s cool to be handy. Tell you what. You do your car’s oil changes, we’ll do your plumbing. It’s a deal!

Still need help? No sweat. Call Muccia Plumbing (201) 343-1414 or just click the following link mailto:info@mucciaplumbing.com