Air in hot water line

Discussion in 'Plumbing Forum, Professional & DIY Advice, Tips & ' started by brianjohns, Oct 29, 2007.

  1. brianjohns

    brianjohns New Member

    Messages:
    4
    When ever you turn on the hot water it spits out of the faucet for a couple of seconds, but it comes out with a lot of force, it will knock whatever your holding on to out of your hands. What is going on here?
  2. Cass

    Cass Plumber

    Messages:
    5,980
    Location:
    Ohio
    do you have a well or is it city water?
  3. brianjohns

    brianjohns New Member

    Messages:
    4
    I have a well
  4. Herk

    Herk Plumber

    Messages:
    547
    Location:
    S.E. Idaho
    I've never seen this phenomenon in a water heater, though it does happen once in a while. However, it is common in boiler systems. Older boiler systems had an expansion tank which was about half full of air, and you had to watch the glass guage on the end of the tank to see that the level of water in the tank remained at acceptable levels because the boiler would "make" air. Heating and reheating the water would release trapped air.

    These days, it's not uncommon to use an expansion tank on a water heater, especially when there is a water pressure reducing valve on the incoming water. But this probably wouldn't solve your problem because these are the bladder-type tanks, and not designed to hold air in the water chamber. You might be able to add an air relief valve similar to those used on boilers, though it might take a little repiping on the hot water side of the heater to trap the air.

    [​IMG]

    The vent would go in the hot water line, but the line should be horizontal, then drop down before going back up to the system, so that air in the line above the heater couldn't get into the rest of the system.

    This assumes that it is indeed air and not steam, that your relief valve is functioning correctly, and so on. One assumes that the heater is separating air from water whenever it's heating, but it tends to build up during the night when the hot water isn't being used.

    In a boiler, air is bad because it can lead to rusting and failure, and I don't know if it would be the same in a water heater, but I think the problem should be addressed, if only to prevent broken water glasses and heart attacks. :)
  5. pking

    pking New Member

    Messages:
    5
    Hi,
    I'm having the same problem. I have a gas water heater, and the air is only coming out of the hot water taps. It's worse in the mornings, but does happen all day. I am also on a well with a pressure tank . The problems started when we replaced our hot water tank. We went from a 30 gallon tank to 40 gallons. Is there maybe something that needs to be adjusted on the pressure tank?
    I've asked lots of plumbers as well as googling this problem, and no one seems to have an answer.
  6. jadnashua

    jadnashua Retired Defense Industry Engineer xxx

    Messages:
    21,917
    Location:
    New England
    Pumping water can entrap air depending on the conditions. If you fill a glass with cold water and let it set for say an hour or so undisturbed, do you get air bubbles on the sides of the glass?

    How you'd get rid of it in the WH, I don't know. Heating it will drive it out, and it would rise to the surface, which gives you the burst of air when drawing hot water.

    I'd also look at all of the pipes and connections to verify there isn't a small leak. It could suck air rather than leak water, depending, too.

    It could be bacterial or algae too, but those are less likely. Their biological process can give off some gas. Does the gas have any smell? Neither CO2 or O2 have any odor.
  7. pking

    pking New Member

    Messages:
    5
    We have had leaks in the past that have been fixed. There is no odor from the air. I'll have to give the water in the glass experiment a try. What will that tell me?
  8. jadnashua

    jadnashua Retired Defense Industry Engineer xxx

    Messages:
    21,917
    Location:
    New England
    That you've got trapped air, and if it weren't for the heating, you'd get spurts out of the cold as well. This could mean that the pump is not far enough into the well or that the well isn't producing fast enough anymore, so it is cavitating and getting air in the lines. Pumps aren't my strong point. See what other comments you get.
  9. pking

    pking New Member

    Messages:
    5
    okay, I did the experiment, and there's no bubbles in the glass, so that's a good thing. I didn't think it would be a well/pump problem.
  10. TMB9862

    TMB9862 New Member

    Messages:
    206
    Do you have an expansion tank by your water heater? If you do which side is it on, hot or cold?
  11. pking

    pking New Member

    Messages:
    5
    do you mean a pressure tank? It's actually right across the isle from the front of the tank, not right next to it. And it's dead center between the hot and cold.
  12. TMB9862

    TMB9862 New Member

    Messages:
    206
    It can't be on both sides. It's either tied into the hot side or the cold side. It should be tied into the cold side. I saw the same thing happen a few weeks ago. Someone put the tank on the hot side and they kept getting air in the faucets.
  13. pking

    pking New Member

    Messages:
    5
    I checked and it's tied into the cold side.
  14. jbissn

    jbissn New Member

    Messages:
    1
    air build up in hot water plumbing

    I have same issue with no resolution - Turn on hot water and 3 seconds of water followed by 20 seconds of air. System is at cottage so usually one week without use. Had water heater replaced (electric) and now have this issue - hot water only. Cold side is ok. On a well but no change to it. No expansion tank or other things different. Never had problen before new water heater. Installer at a loss - has never seen issue. Need some help. Thanks.
  15. henkfish

    henkfish New Member

    Messages:
    2
    Location:
    Muskoka, Canada
    air in hot water lines

    Hi:

    Same problem. Some time ago I came across a post or two from Alberta, where methane gas in water wells is apparently a problem. they suggested installing a Honeywell Braukmann valve in the hot water line. I did that, and the problem went away for quite a while...but now it's back, and I am getting a bit tense about it again (well my wife is:)). Still, I'd like to know if there is any maintenance you need to do with these valves. any ideas? Pump seems to sucking air/water mix at startup, then settles down to pure water, it seems - different sucking noise. Well is actually higher than pump - worked fine w/o a foot valve - go figger, so priming is definitely not an issue. Incoming water line is HEAVY duty, through sand, and part of it is under the deck, etc.....don't want to go there. Otherwise system works fine. Water is acidic and contains much iron = welcome to the Canadian Shield, and we are on our fourth (count 'em) fourth, water heater in 5 years - but this one seems to be working better than the others, in that the hot water is not yet brown...though I suspect it will do so in time as the anode is eaten up and the water attacks the tank.

    Does this wound like a tale of woe or what? Any advice on the Braukmann valve will be welcome.

    thanks
    Henk
  16. MACPLUMB 777

    MACPLUMB 777 TROJAN WORLDWIDE SALES RP

    Messages:
    679
    Location:
    Houston, Texas, United States
    Gas, gas, gas ! ! ! In hot water line

    Note to all;
    what you have is a hydrogen gas build up in your water heaters !

    This is caused by a reaction between the water and your andode rod

    after the water heater has been setting for some time ! !

    I will post a link when i find it on the net

    HERE IS A LINK TO A HOME INSPECTORS WEB SITE THAT TALKS ABOUT,
    http://www.nachi.org/forum/f22/hydrogen-gas-build-up-dormant-water-heaters-4298/

    AND YES THIS HAS BEEN KNOWN TO CAUSE EXPLOSIONS
    Last edited: May 26, 2009
  17. henkfish

    henkfish New Member

    Messages:
    2
    Location:
    Muskoka, Canada
    air in hot water lines

    Oh my, what you can't do when you find the instructions!! I found the sheet that came with the Braukmann valve, and have carried out the suggested maintenance - let's wait and see if the problem is still there tomorrow morning. It only happens in the first use after sitting all night. The valve did not appear to be all that dirty, but you never know.

    cheers

    Henk
  18. MACPLUMB 777

    MACPLUMB 777 TROJAN WORLDWIDE SALES RP

    Messages:
    679
    Location:
    Houston, Texas, United States

    Attached Files:

    Last edited by a moderator: May 26, 2009
  19. jadnashua

    jadnashua Retired Defense Industry Engineer xxx

    Messages:
    21,917
    Location:
    New England
    There's a difference between having methane or similar flamable gas in your well water and your water creating a reaction in the WH to produce hydrogen. If your water is making the hydrogen, selecting a different anode rod can help, but if it is in the water from the beginning, it won't. Both can blow up things, but the hydrogen flame is much harder to see and the flash point is lower...hydrogen really likes to make water - it burns very easily.
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