Hot water problem

[Wayne Docimo]

About a year ago I replaced the hot water tank which sprung a leak with an on demand unit. The water from the tub sprout never put out really hot water luke warm at best. The shower did put out hot water. Now the shower is putting out luke warm water. I changed the stem valves on the hot cold and center knobs yesterday but still luke warm. Is it possible that the shower and tub have a high gallon flow rate that the on demand unit can't heat fast enough? This an old system with a knob or faucet for hot and cold as well as a faucet to change from tub to shower. I also changed shower head but same problem. The rest of the sinks in the kitchen and two bathrooms still get plenty of hot water. I'm thinking maybe i should have put another hot water tank in place of the old one because I never had a problem with hot water anywhere until it sprung a leak. What do you think it could be?

Thanks
Wayne

 

[Diehard]

Well if nothing else you should know of find out what your tankless is rated for. Foe example GPM at a given temperature rise. It is based on the incoming cold water temperature and the rate of flow. A tub spout is probably the biggest flow rate in the house. The shower shouldn't be more than about 2.5 gpm.

Sounds like you may have problem with the shower control.