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Rinnai Tankless Water Heater

I have a Rinnai Continuum Model 2532 tankless water heater.

When we turn on a faucet and demand hot water, the unit makes a loud horn blowing deep trumpet sound for a couple seconds and then stops.  The water is hot and the unit works fine and gives us all the hot water we want, just makes this extremely loud noise at start up.  This only happens when the ground temperatures change and the water going into the heater is much colder, typically 40 degrees outside.  Never happens in the summer months.

Your help is greatly appreciated.




  • lchmb
    lchmb Member Posts: 2,997
    build up

    It could be sediment building up in the unit. I would suggest you get someone in to take a look at the unit and at least do a service to check it over.
  • Jack
    Jack Member Posts: 1,047
    It being a 2532

    it is probably 5 yrs old. It would be worth flushing the unit with 4-5 gallons of white vinegar. Using the service valves, pmp from cold thru to the hot side. Do not pump from hot to cold! Your description of the issue is a classic for an undersized gas line. The rumble etc. The unit is trying to fire and does so, but with a winter load, on your house and the whole system, the gas pressure is just a tad low. Teh unit knows what it wants to do but air fuel mixture is compromised and it will sing. If you are lucky it will sing a tune you like, but I've not found that yet. In the summer with reduced demand on the gas supply system the unit can do its thing.

    BTW, when you flush it, make sure to clean the immersion sensors at the upper rt and at the hot water outlet. Two small while wires connect them. There is a very small O-ring on the sensor. Don't lose it;)
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