Slow hot water

[Paul Myers]

Dear Forum,

A recent re-model included changing from a hot water tank to a Noritz Tankless. It was installed by a professional plumber... Fixture units were all accounted for and the tankless was sized accordingly. The tankless is centrally located to bathrooms and kitchen... The guest bathroom is only about 10 to 12 feet away from the tankless. It takes about a minute and a half for hot water to reach even the closest sink. Does that sound normal? Is there an adjustment within a tankless unit that informs the unit when to fire up? Could that initiation be delayed for some reason?

Thank you. Terrific forum.

 

[Terry]

It's pretty common for tankless to have a delay. It runs water through the unit, takes a reading on the temperature of the water and produces flames to heat the water to 120 degrees. A tank is already heated to 120 and is ready to go much quicker. At least the tankless never runs out of hot water.

 

[Sponsor]

 

[Reach4]

Does that sound normal? Is there an adjustment within a tankless unit that informs the unit when to fire up?

Test with the aerator removed. If that warms up acceptably fast, replace or modify the aerator cartridge to flow more.

 

[Plumber69]

usually the first complaint I hear after these are installed.

 

[Jadnashua]

With a tank, regardless of whether it has heat traps in it, the pipes above it get warmed a bit. Then, the water is immediately hot coming out verses the delay. With a tankless system, it will have a flow sensor in it. It's essentially off and there's no hot water stored inside. Once the hot tap is turned on, and the flow sensor sees a big enough flow (that's usually in the 1/2 gallon/minute range), it only then turns the burner on. That takes a moment to heat up the heat exchanger before it is actually heating any water (but it's fairly fast). So, there will always be a delay, and if you're only drawing a small amount - say you have the faucet set for warm and maybe not full strength, it may never get enough flow to trigger the tankless system to turn on and it will always stay cold.

There are a few tankless designs that have a small internal tank that can overcome those limitations, but they won't be as efficient, just more convenient. They may also have an internal pump to move hot water into that tank, which adds to the complexity and therefore cost and maintenance. There's no free ride. If your incoming water never gets super cold, you may never run out of hot water with one, though, assuming it is sized properly. Can't say that with a typical tank installation.