Intermittent Hot Water

Discussion in 'Plumbing Forum, Professional & DIY Advice' started by obsidian97, Dec 28, 2008.

  1. obsidian97

    obsidian97 New Member

    Sep 23, 2008
    Hi all,

    We moved into the house less than a year ago, and recently (a few months back) replaced the 30 year old (amazingly) gas hot water heater with a new 55gal AO Smith gas model plus a cold water expansion tank.

    The issue we're seeing since then is that we occasionally get almost no hot water at times. For example, this morning, my wife took a shower with next to zero hot water. About 10-15 minutes later I took a shower in the same bathroom and had excellent hot water.

    I haven't noticed any warm water coming out of the cold water side of any of our taps, and it's not a first-thing-in-the-morning type issue either. Our son takes a bath everyday in the evening and sometimes it's really hot, sometimes it's barely above cold. It's from a different tap than our shower. I typically have excellent hot water in the kitchen sink before we run his bath.

    I'm not aware of any restrictors on any of the taps. Every faucet in the house except one is single handle. No recent plumbing changes other than the new hot water heater.

    We never had this problem before the hot water heater was replaced. It doesn't seem to be tied to the recent cold weather either. The outside run for the hot water pipe in the garage is very short, and we're talking about bathroom faucets running for several minutes. I've gotten a tub full of lukewarm water in the past.

    It sorta sounds like there might be a bad faucet because it's not consistent, but a tub-full of lukewarm water or a 5-10 minute shower's worth followed by a perfectly normal bath/shower?

  2. WV Hillbilly

    WV Hillbilly New Member

    Aug 1, 2008
    Sounds like the thermostat on the new heater isn't working properly .
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  4. obsidian97

    obsidian97 New Member

    Sep 23, 2008
    I wondered, but it seems like the heater would be hard pressed to go from luke-warm for 10 minutes solid, sit for 10 minutes, and then be piping hot for 10 minutes if it hadn't been running normally.
  5. Verdeboy

    Verdeboy In the Trades

    Jun 12, 2006
    That water heater is still under warranty. The manufacturer should send someone out to look at it at no charge.
  6. Redwood

    Redwood Master Plumber

    Dec 15, 2007
    Service Plumber
    Sounds like a bad thermostat to me too!
  7. Nedbrod

    Nedbrod New Member

    Dec 10, 2008
    trades supervisor
    new jersey
    I'm in agreement that it seems like a lazy thermostat but I would also check to make sure of two other things. First, look at the top of the water heater and make sure that the cold water supply is going into the cold water connection of the water heater. The second thing would be for the plumber to confirm that the delivery tube located in the cold water supply connection of the water heater is intact. Depending on the timing and amount of hot water being drawn from the tank it could be short cycling if the delivery tube is damaged or missing. I had a similar problem once before and found the delivery tube was only about 12" long and was not sending the cold water to the bottom of the tank. Good luck!
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