What causes air in water pipes?

[googlemail2003]

I've already posted this, but I screwed up the Subject line. My
husband passed away recently and my brain is only on half power.
Also, he used to take care of these kind of issues. Sorry about the
multiple postings
Question:
I noticed that within the past month or so I have a lot of air when I
turn on the hot water. As the water gets warmer the air gets worse.
Since it's only the hot water I assume it's a problem in my house, but
just to be sure I checked with my neighbors and the do not have any
problems. We have town water.
What could be causing this? The air comes out in strong bursts
sometimes and it makes the pipes vibrate.
thanks.
Jane

[Eric in North TX]

My first though is a defect in the water heater. Air in pipes is common after work is done, but I've never seen it last more than a couple of days & only a couple of minutes if you go around and run everything.

[HeyBub]

And we are sorry for your recent loss.
Wild guess: You have a defective thermostat on the water heater (or it's set way too high) causing the water to boil. It is extremely unlikely that the pressure would build sufficiently to rupture the tank, but it's not impossible. You'd have to have TWO things wrong: the bad thermostat AND a defective pressure relief valve. Still...
Another clue supporting this theory is the temperature of the water. If it is REALLY hot - like steaming - the symptom lies with the water heater's thermostat (probably). It IS possible the thermostat's temperature setting got bumped when someone tried to store something next to it. Try turning it down.
Alternatively, if you're on a well, it could be pumping air into the system - Nah, never mind, if that were the case you'd be getting air in the cold water line also.

[Sam]

[Bob F]

If the hot water pipe comes out of the top of the coldwater pipe, it could be taking all the air in the water, leaving the cold un-aerated.

[dpb]

...

Indeed...

That's what the safety relief is for, and if it were boiling any significant amount it would lift.
But, it could still be either maladjusted or malfunctioning and hotter water will cause more air out of solution plus perhaps more nucleate (localized) boiling on the heater (assuming electric) element(s)...
So agree first question is "is it hotter than normal?"
--

[sligoNoSPAMjoe]

I am sorry for your loss and I see that you have received some good advice. I will only add one thing. You have been trouble shooting this thing very well and you provided all the information that most people would not have included allowing someone to give you some answer.

[YvonneD]

No, the water is not hotter than usual. In fact I was thinking of asking them to set the temp higher when they come.
Also, it is not well water. I use Town water.

[YvonneD]

Thank you.
I do plan to have the plumber here within the next week or so. I just would like to have some idea of what might be wrong. I hate dealing with these things in complete ignorance. Sort of like taking the car in for service and not even knowing how to check the oil.

[HeyBub]

I admire your diligence.
The air has to be coming from somewhere! If the water's not too hot, it's not steam. If you don't see the same thing on the cold side, air is not being pumped into your system from the supply lines.
The only other thing if COULD be is a miracle - or the opposite: a demon. In either case, I'd call the Church.
Just on the wild side, ask your neighbors if they have any funny business with their water supply. Can't hurt to ask.

[Winston]

Could be cavitation.
Any valves connecting water to your heater should be 'full on'. That is to say, the handle(s) should be turned counterclockwise till it stops.
Here, a homeowner has turned off the 'inlet' and 'outlet' valves before disconnecting the water supply.
Beware that the top of the heater will be HOT so use caution and think about the consequences of an involuntary flinch. Test first with the back of your hand and please stay clear of the exhaust stack poking up from the middle of the heater.
--Winston

[Winston]

(...)

Let me correct myself.
The photo shows control valves for a parallel water heater, not the valves I was indicating. Still, the principal is the same. A restriction in the inlet side of your water heater could cause creation of air bubbles, so any valve(s) providing water to or from the heater must be fully open, to minimize this cavitation.
--Winston

[E Z Peaces]

Hello Jane,
Steam bubbles wouldn't reach your faucet unless your tap water was boiling hot.
Water tanks have anodes to keep them from rusting. Anodes produce bubbles of hydrogen and oxygen. It happens faster with soft water. Some anodes are designed to slow the bubbling.
I'll bet you aren't using as much hot water lately. That gives the gas more time to accumulate.

[HeyBub]

Excellent diagnosis!
You could probably test this by holding a match under the faucet.
No, wait...

[YvonneD]

I use very little hot water lately. You could be right. Anyway, the plumber is coming next week.
Thanks for the response.
Jane

[YvonneD]

Thanks.
Actually I've had some air in the cold water pipes too. That's been going on for over a year and doesn't seem to happen in the winter. Maybe it is from the main inlet, although my neighbor across the street doesn't have this problem.
The plumber is coming next week.
thanks again.

[E Z Peaces]

Maybe it's related to a strange experience I had a couple of years ago. Does your hot water look milky?
My hot water supplies four sinks, a washer, and a shower. One day when I drew some hot water in a glass at the sink in the main bathroom, tiny gas bubbles made it look white. The water slowly cleared as it sat in the glass. I tried it again. Still white. I removed the aerator. Still white. After I drew more than a quart, it still wasn't clear. It was clear the next day and ever since.
I wonder if the white appearance came from tiny bubbles of hydrogen and oxygen that had been dissolved in the water until I reduced pressure by opening the tap. I don't know why the water with the dissolved gases would have collected in the pipe to that tap.
If more gas had accumulated in the water, perhaps it would have sputtered from the tap. I wonder why the water was cloudy that day but not before or since. Could something unusual in the town water that day have increased gassing in my water heater anode?

[Hustlin' Hank]

Air in water lines that are on city water can be a common occurence, especially if you are at the end of the main line. When the pumps loose power due to an electrical outage, or other reason, air is produced thru what is called "cavitation" in the pumps volute. If this is the case, there is not much you can due about it, other than contacting your water company and see if they can (or are willing) to either reduce the pressure slightly or take other measures. They way want to know about your problem in order to maximize their delivery and avoid other problems. Anyway, check with them before you call a plumber.
Hank

[HeyBub]

Not too many, if any, municipal systems use pumps to supply the water mains. They use pumps to fill gravity-fed tanks. This has several advantages:
* They can use a smaller pump and have it run when demand is low to get ahead of the curve * The water distribution system still works - for several days - if the electricity goes off or the pump fails * A gravity system maintains a constant and predictable pressure
I've got a relatively new water reservoir right down the street. It's 60' in the air of course but the sucker is HUGE. The pole on which it stands is round, concrete, and about 30' in diameter. The tank itself is also concrete, about 60' in diameter and twenty feet high and must contain about 4.5 million gallons!
Every time I pass it, I think it would make a really swell dwelling with just a few additions: Elevator, windows, gun ports, etc.
Here's what it looks like:

[dpb]

...

What a bunch of mostly hooey...
And, even if it were, air in supply lines would show up in both hot _AND_COLD_, not hot only...
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