No hot water pressure


Old 11-18-18, 12:33 PM
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No hot water pressure

In our previous home, we would occasionally run into problems with no hot water pressure. You’d open a tap, hot water would run for 3-4 seconds, then stop completely. Never any issues with cold water pressure. I would run faucets, bang on pipes, drain the hot water tank a few gallons.......and I would eventually hear a loud bang and the hot ater pressure would return.

Happened for years. Felt like it usually occurred after I started the lawn irrigation system each spring. Figured it was dirt somehow getting lodged in the inlet pipe to the hot water tank. Anyway, never got it figured out and moved outta there. It was an occasional nuisance, but not terrible.

Fast forward a few years. My brother has just started having the same problem. He doesn’t have any irrigation systems. No hot hot water pressure for awhile...then, loud bang, pressure returns. Has happened 3-4 times to him over the course of a month.

Technician comes in and says there is a check-valve in the tank that prevents water temps mixing? Something called a “tadpole”? Apparently the tech pushed the tadpole out and into the bottom of the tank. Apparently, it’s not “required” and without it, the hot water temp could be slightly hotter. Could be caused by hard water buildup.

Btw. Both tanks are heated by gas.

Does any of this make sense? Is there a check valve in the tank? Where? What is it’s function?
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Old 11-18-18, 06:13 PM
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Where are you located? What country? I have never heard of anything like this in the USA. I think I would consult a plumber.
Old 11-18-18, 07:31 PM
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Some water heaters come with "heat trap nipples" which look almost the same as ordinary nipples for connecting the water pipes on top.

The heat trap nipple has something like a check valve and it is used to inhibit eddy currents within the nipple that can cause a minute circular flow of hot water up out of the tank where it cools down and sinks back into the tank. Over time heat is lost and the burner/elements have to come on more often to keep the water hot..

Depending on the technology the check valve could get stuck closed.

They can be interchanged with ordinary nipples.
Old 11-19-18, 04:30 AM
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Thanks. This sounds like the issue. Heat trap nipples. I’ve done some research. It also explains why I would hear a clicking sound when taps were closed. It’s the little ball dropping back into place. Always thought it was water hammer and I spent hours trying to cure it.

Some basic info here.
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