Banging Zone Valves

It sounded like someone was coming through the front door with a fire axe.

We were sound asleep and then it arrived, as it did night after night, all winter long. BANG! I came rocketing up out of the covers and so did Marianne, and then she looked at me as if all of this was my fault, and that’s because I am a husband. Mechanical noises within a house are almost always the responsibility of the husband. “Do something about that,” she hissed.

So I looked into it.

I asked around and even paid a visit to the factory where they made these valves. Wonderful people. Very gracious hosts. We sat in a conference room and chatted about things hydronic. I told them about our sleepless nights and the wrath of The Lovely Marianne, and how they were fortunate that it was me and not she paying the visit. They listened attentively, and looked at each other, and they took notes. They nodded sympathetically. Then they told me that I was the first person to ever bring up this problem. They were mystified and quite concerned. They would look into it immediately and get back to me.

I waited a year.

I called one day, just out of curiosity. I had already solved the problem at home by having the valves replaced with circulators. I was just curious at that point as to why they had never gotten back to me. They had said that they would. When I called I learned that the folks I had met with on my visit weren’t there any more. They had moved on to other areas of this vast company. But there were new people who had taken their places and these new people were very interested in listening. So I explained what had happened. They told me that was the very first they were hearing of a banging problem with zone valves. They were going to look into it and get back to me immediately.

I wait.

I know what makes the zone valves bang. This one is a normally closed valve that’s powered open by a motor on a call from the thermostat. There are two small, but powerful, springs that pull the valve closed. The thermostat signals the motor to open on a call for heat, and when the valve is fully opened an end switch starts the circulator and water flows into the zone. When the thermostat is satisfied, it cuts power to the zone valve’s motor and the valve closes on its two springs. As it does, it trips the end switch and stops the circulator. Standard stuff.

The banging begins when two zones are calling at the same time and then one zone valve decides to close while the other is still open. As the valve closes on its springs the other valve keeps the circulator running because it still needs water. The velocity of the water flowing through the closing valve increases as the gap narrows. That water gets going really fast just before those two tough little springs pull the valve to its final closed position. And when the water hits the brakes, Newton’s Law kicks in – literally. For every action, there’s an equal and opposite reaction. In our house, the action was the sound of someone coming through the front door with an axe. The equal and opposite reaction was the look on the face of The Lovely Marianne. Very scary.

And not a week goes by that some homeowner doesn’t come to, find my email address, and drop me a note about this loud banging in their hot water heating system. It’s keeping them up at night. I write back and ask if they have these zone valves and they always say yes. Then I tell them that they’re the first people on earth to have this problem, and that I’ll get back to them soon.

Not really. What I do is give them the unofficial advice that some of the factory reps have given me over the years. This advice is always prefaced by a quick glance around to make sure management isn’t listening. “If a valve bangs,” they say, “disconnect one of those little springs. That will cause the valve to close with less force and solve the problem once and for all.” This didn’t work in our house, though.

I once asked a factory rep why they just didn’t leave the second spring out of the valve. That would save them money and make the world a quieter place. He told me that there was no need to do this because there was no problem. I was the first person to ever bring it up.

You can’t make this stuff up.

When I’m talking to a sleepless homeowner I might also suggest (because a rep suggested it to me) that they have their system repiped, putting the zone valves on the return side of the system where they will be further away from the full power of the circulator. That shouldn’t cost much to do. Right?

A guy I know invented a little electronic device some years ago that kills the power to the circulator if any zone valve tries to close. It then automatically restarts the circulator to meet the needs of the zones valves that are still calling. Brilliant! He brought this device to the folks who make the zone valves and suggested that they buy the rights to produce it from him. It would be a wonderful addition to their product line, and it would solve the problem of the banging zone valves once and for all. They listened attentively, took notes, and then told him that there was no problem with banging zone valves. He was the first to mention it.

For years, I sent the homeowners to this guy, but he has now moved on to other things. He sold his last anti-water-hammer widget a year or so ago and that was that.

I solved the problem in our house by using circulators. The Lovely Marianne sleeps well nowadays, and so do I. We moved on.

Should you encounter this problem at any time in your life, however, rest assured that you are the very first. I have this on good authority!

Dan Holohan

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