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Air from hot water after using washing machine

I have an electric low-boy 40 gal hot water heater that I installed in 1999. This was a rental property that I now live in and I never got a complaint about this problem from any of the renters. The water heater is not leaking and is functioning properly with the following exception. After I do a (full) load of laundry I get a second or two of air when using any of the hot water taps.

This only occurs after the first use of a tap (kitchen faucet, bath faucet, or tub faucet that is all the faucets in the house, one each.) At no time do I get air from the cold water faucets.

At first I thought that I may have hooked up the water pipes wrong (cold line to hot outlet and hot line to cold outlet) but I checked them and they are correct. For the life of me I can not figure out how using the washing machine can be causing air to get into the hot water lines. I usually only wash laundry once a week and after the air is bleed out with the first use I have no problems until I use the washing machine again.

The real interesting part is I lived across the street in a house that is the same size and floor plan as this house and replaced the hot water heater there at the same time as I replaced this one and never had a problem like this over at that house.

BTW water supply is from city service, not well service and these houses are all electric, no gas. Have you run into this before?

Re: Air from hot water after using washing machine

Is there perhaps a sillcock/outdoor faucet or similar tapped off the cold water supply pipe prior to where it hooks up to the water heater? If so, this *may* be the source of the air. If the washer in that sillcock is "weak", it may be getting sucked inward (or out of place) a bit when cold water runs thru the line (venturi effect) and the air then ends up collecting inside the water heater.

Since the water heater is a large vessel where water stands/lingers for long periods of time, even a minor influx and subsequent mixing of air with the water is likely to show up there...but not be noticable in the cold water lines of the house because they simply don't have the capacity to hold enough water for the problem to evidence itself there to any real degree.

If there is no such sillcock, I might start suspecting a perforation somewhere in the supply line of/to the house or a "weak" gasket/washer somewhere else (but still prior to the water heater), maybe even at the meter or perhaps at the pressure reducing valve if you have one of those.

Re: Air from hot water after using washing machine

There is an outside faucet/sillcock however I am not too suspect of it. Given your description it wold seem possible that that is where the air is entering however there is at least 4 ft of pipe that would have to fill with air before it got into the line feeding the hot water heater. But it is worth checking out.

If there was a leak in the supply line I would suspect that I would notice it in the cold line as well but I do not. Also since I am in Texas and we are in drought conditions it would have to be a mighty small leak or directly under the slab for it not to eventually be noticed. I sure hope that it is not that.

Thanks for replying.

Re: Air from hot water after using washing machine

Just a thought , if it always happens after using the washer then it sounds like the washer or it's associated plumbing is the source of the air.

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