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Starting Member


Saturday, June 26th 2021, 4:19pm

Zone Surging

My system is around 15 years old. This year on startup up, all my zones work normal but the last 2 are surging. They come on fine and run for a couple of minutes and then will surge for probably 15-20 secs and run normal again for another few minutes then surge again. What could be my problem. I’m on city water with no pump. TIA.


Supreme Member

Posts: 5,381

Location: Metro NYC


Sunday, June 27th 2021, 2:40pm

The first thing to check is the supply valve. Is it completely open? Is there a partially closed valve anywhere in the water pathway?

Second thing to check, are the zones you said are surging otherwise behaving normally? No leaky heads? No breaks in the lines?

What the questions are pointing at, is a situation where zone valves, when older (but not always older), can react to a dip in supply pressure in a way that causes the zone valves to almost close. The almost-closing zone valves make the supply pressure rise, and the rising pressure re-opens the zone valves, causing the supply pressure to dip, which leads to a vicious circle of surging pressure.

If there are no supply restrictions, and the zones are functioning normally (excess flow makes the situation worse) then you look to replace the zone valve diaphragms. Doing all of them at one time is the best plan, because it resets the clock on your zone valves.

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