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Question DetailsAsked on 5/21/2016

Why am I having air surges from the hot water only after replacing shallow well jet pump?

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If you did not open up and flush out all your lines after the pump replacement (assuming the household lines were not valved off at the pump so they partly drained out) then you could have water in the lines for several days. Commonly takes about 3-5 minutes full flow at each faucet/usage point to clear out the air in a line. And initially, if the water heater was partly back-drained by siphoning into the cold water lines, draining the bulk of the air out of it using the temperature/pressure relief valve at the top side.

Of course, if the pump is pulling air through a leak in a fitting or in the inlet line, an open bleeder valve, or there is low water level in the well it will put out air until the problem is fixed. A restricted foot valve in the well can also cause formation of air in the pipes due to cavitation.

I would guess the reason you are getting most of the air in the hot water line is that the water heater line is the first line off the incoming cold water supply line - especially if it comes off the top of the pipe - so the air preferentially goes up into that line to the hot water heater rather than through the rest of the household cold water line.

Another possibility is you have an expansion tank for the hot water heater (very common) and it either does not have a bladder at all (in which case probably mounted at or in the overhead floor joists) or you have a smaller more modern type with air bladder and it filled with air because the pipes drained out when the pump replacement was being done, and is gradually bleeding the air out into the line to the water heater over time. Or the bladder ruptured and the entire tank is full of air.

A third possibility is you have a hot water circulating pump for constant hot water in the system, and that was allowed to keep running while the lines drained partly during the pump replacement, so the pump had damage from dry running and is now cavitating, which causes air bubble formation. If that is the case, it would almost certainly be running much noisier than usual.

A fourth possibility for the source of the air is a shutoff valve at the pump line is mostly closed, causing cavitation as the water jets through it, which forms air bubbles. Would most likely be noticeable as reduced flow from faucets.

A fifth possibility for the air formation (though not directly causing the hot-only issue discussed above) is the jet pump was not thoroughly primed before starting it up so it is cavitating internally due to trapped air - a very bad thing for it.

If you have a faucet or drain valve between pump and house or right inside the house before the cold line splits off to household and water heater, put a hose on it and run it into a bucket (so you can see the bubbles clearly) and see if the incoming water has a lot of air in it - if so, something wrong at the pump/well end and a Well and Pump contractor (probsably one who installed the pump) is who to call.

If the incoming water is essentially air-free, then flush out the hot water lines to all usage points, and if that does not stop it start looking for trapped air in expansion tanks or in the top of the water heater - or possibly coming from a water treatment system that siphon drained out in the process.

Answered 2 years ago by LCD

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