Air in water lines

proudgm_03May 10, 2009

What would cause you to have air in your hot water line? Everytime we turn on the hot water the faucet sputters and spits. This doesn't happen if we only have the cold water on. Thanks!

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funny, the same thing happened to me this morning. Flushed the toilet and it soundied like it coughed. Flushed again, OK. Turned on the water in the sink, coughed again. Later it was fine. I wonder if the water company was up to something over night?

    Bookmark   May 11, 2009 at 11:19AM
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If you have a vacuum relief valve on your hot water heater, this would introduce a small amount of air into the system. That would cause the spigot to spit when first turned on. This would be most likely, lets say in the morning, after the water usage sat idle for a while. An expansion tank possibly could cause the problem also. With a well system, there are a few other causes.

    Bookmark   May 11, 2009 at 7:52PM
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It's a well system. Any ideas?

    Bookmark   May 12, 2009 at 4:59PM
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Residential water systems pressure ranges from 45 to 80PSIG. Note, the designation PSIG, the G means "Pounds per square inch Gage", or in layman's terms it means pounds per square inch above standard atmospheric pressure. Now, given that the pressure in the tank is always greater than atmospheric pressure, it then stands that it is physically impossible for a vacuum breaker to introduce air into the hot water system unless the tank was drained before the problem occurs. Any opening, no matter how great or small would manifest itself as a leak, simply because the code minimum pressure in the water system is more than 3 times greater than the atmospheric air pressure surrounding the tank.

It is possible for an expansion tank to introduce air into the hot water system if the internal diaphragm leaks but in that case, within a few days the air chamber in the expansion tank would become saturated and you would see water leaking from the Temperature & Pressure Relief Valve.

The original post states that this problem occurs every time they use the hot water, but not when they use the cold water. If the water heater is installed to code specification that is a physical impossibility. The plumbing code states that the only valve permitted between the hot and cold water supply is the "cold water shutoff valve" on the cold water input line to the water heater. When the cold water supply valve is open there is a direct connection between the hot & cold water systems, and the pressure in both hot & cold water distribution piping remains equal.

In a standard municipal supply system, when thermal expansion occurs in the water heater a volume of water equal to the expansion back flows into the cold water line and ultimately out through the house water supply line to the municipal main, however even when that thermal expansion occurs the pressure remains equal in both the hot and cold water distribution systems.

When the municipal static head pressure to the structure exceeds 80psi we are required to install a PRV (pressure reducing valve) on the cold water supply line. Most PRV's have check valve feature built in so we are also required to install an expansion tank on the cold water supply line to the water heater, but here again, even thought the expansion tank absorbs the thermal expansion as the water is heated, none-the-less, the pressure on both the hot and cold water systems remains equal.

Home well pumps also have a built-in check valve, therefore we are required to install an expansion tank on the cold water supply line in the close proximity of the water heater, however, here again, the pressure remains constant on both the hot and cold water systems.

This then leaves us with two possibilities.

1. Someone foolishly installed a check valve on the water heater supply line.
2.The house is supplied by a well pump and the water from the well has an excessive amount of entrained air, which is being released by the heat. Generally this indicates either a problem with the water or the pump is not deep enough in the well.

Andrelaplume2 stated that they had air sputtering out of the faucet this morning, but it was an isolated case and not representative of normal operation. They went on to say that perhaps the water supply company was up to something overnight. You are correct, it is quite possible that they had to open the main to make a repair and in the process air got into the line, In that case the problem will correct itself in a very short time.

    Bookmark   May 12, 2009 at 8:59PM
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A vacuum relief valve is designed to let air into the system to prevent several forms of damage. Do a Google search for "Vacuum Relief Valve" and you will find plenty of info on why they are installed and what damages they prevent.

If you have a bladder type pressure tank, the air chamber may be leaking...check the air pressure in the tank. Also, if your check valve is leaking and a bit of the water drains back to the well, air can be introduced via the vac. rel. valve or any leaking faucets.

    Bookmark   May 12, 2009 at 10:10PM
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With everything you have said I would say its your hot water heater release valve. They tend to sometimes get mineral deposit build up which can cause some simple problems. Go to your hot water heater and find the water line that feeds it water. Usually this will be a copper line coming up throu the floor and will enter the tank about a foot from the top of the tank. The release valve is usually metal silver color about an inch long and will be where the water line enters the tank. To open the valve you flip it out so its pointing away from the tank. Flip it several times out and back in, this will move the gasket inside so if there is build up it will hopefully dislodge the build up.

    Bookmark   May 14, 2009 at 3:58PM
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I've got this problem too. I have a well. Does anyone think
it could have anything to do with the heating elements in
the hot water heater?

    Bookmark   February 19, 2011 at 10:46AM
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"Does anyone think
it could have anything to do with the heating elements in
the hot water heater?"

If there is excess air dissolved in the water heating it will force it out of solution.

    Bookmark   February 20, 2011 at 12:12PM
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I have a similiar problem on both hot and cold.It dissappeared over the winter months here in the northeast but has returned after the spring thaw has started. especially after a moderate rain. Submersible system

    Bookmark   March 21, 2011 at 9:06PM
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Proudgm - I am sure you have long ago solved your problem, but for anyone else reading this thread that has a well-based system: the #1 cause of air in the lines is a faulty pitless adapter. The pitless adapter is about 4 to 5 feet below the ground surface on the well pipe. It's purpose is to convert the vertical feed from the pump to a horizontal feed into your home. The pitless adapter has a rubberized seal on the vertical portion that "slips" into the pipe-mounted adapter frame. Those seals get hard and fail over time. Here's a simple test: take the cap off of your well pipe. Run the water in your sink until the pressure regulator turns your well pump "on". After the pump has shut off and your system is fully pressurized, listen to the open top of your well pipe. If you hear hissing, the pitless adapter seal is faulty. You can replace this yourself, but I would highly recommend you contact a plumber. Save some money by digging down to the pitless adapter. Hope this helps someone.

    Bookmark   April 1, 2011 at 7:40PM
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"Save some money by digging down to the pitless adapter."

Save your back. You don't need a shovel to remove a pitless adapter.

    Bookmark   April 2, 2011 at 1:50AM
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I know this is quite an old thread, but I'm having the same problem. It only started after the hot water heater was replaced 3 months ago. We're on a well and the hot water sputters, but it only seems to happen after the water heater has run a heating cycle. The first fixture to run (bathroom, shower, kitchen, doesn't matter what, just the first one) sputters, then all other fixtures are fine until the water is heated again.
The old natural gas heater was a 12 year old 50 gal and I switched to 40 gal NG. I never had this problem with the old water heater since it was new. Any ideas would be appreciated. Thanks!

    Bookmark   February 15, 2014 at 2:42PM
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If the temperature is set to high it could cause the water to be close to boiling.

It could also be from when the installation was performed. Air was introduced into the hot water plumbing and is slowly finding it's way out.

    Bookmark   February 20, 2014 at 12:32AM
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