On demand hot water heater leaking

You will have to take the case off and look for where the leak is . Then replace that part .

Most on demand or tank-less units require a minimum flow rate before the unit will fire up, they designed them that way so small water leaks (drips etc.,) keeps the unit from going on needless;y. Try opening the shower hot water fully and see if it comes on, If it does, try closing it slowly to see where it shuts off. Make sure your shower head is clean and not blocked with calcium, which will restrict the water flow. You could also try changing the shower head to one that allows more gallons per hour flow rate. Also make sure the cold inlet and hot outlet valves on the unit are fully open and the diverter on the shower is fully open as well.

Hi -

If your water heater is working (ie: making hot water) then most likely your heater isn't leaking. Rather, the leak is coming from the cold water supply and running down the tank where you see it at the bottom of the tank. A working tank that is leaking would produce a leak of hot water - not cold. You should carefully check the cold water piping for a leak, drip or stream of water and make the required repairs.

TP valve is dripping? Or drain valve is dripping?
Or water heater is rusted out?
http://waterheatertimer.org/Leaking-water-heater.html

Gene

If you need further help, I’m available over the phone at https://www.6ya.com/expert/gene_9f0ef4df2f9897e7

Probably bad news if steel tank is leaking.

1) Copy following link for do-it-yourself troubleshoot walk-thru:
http://waterheatertimer.org/Leaking-water-heater.html

2) Drain tank and set in a drip pan with drain line to outdoors.
http://waterheatertimer.org/images/Water-heater-drip-pan-2.jpg
http://waterheatertimer.org/Water-heater-will-not-drain.html

3) If tank ruptures, it will flood home

If you need further help, I’m available over the phone at https://www.6ya.com/expert/gene_9f0ef4df2f9897e7

it sound like you are over heating the unit

I recommend safety changes to prevent ruptured water heater and assorted leaks.
135 degree hot water.
Maybe replace TP valve if it is dripping.
Drip pan under water heater with 3/4" drain line to outside.
Expansion tank on incoming cold water line to absorb pressure build-up, and prolong life of tank and plumbing.

Here's why:

1) Yes you can have scalding hot water.

2) I recommend 135 degrees since that will burn the evil right out of ya. And generally kill clothes washing bacteria.
http://waterheatertimer.org/How-to-adjust-water-heater-temperature.html

3) 150 is dangerous and can seriously burn skin in 1.5 seconds. Not safe around children and elderly.

4) Temperature settings on electric water heater are approximate, since thermostats are calibrated approximately, and read temperature through tank wall.

5) Also if you want to increase amount of hot water for high-consumption household, then setting tank temperature upward is one solution since more cold water is mixed with hot, so amount of hot inside tank goes further.

6) High temperature can cause TP valve to release water.
TP valve is pressure-temperature safety valve. Do NOT cap off.
Rating should be 125 psi and 180 degrees ... but all things water heater are approximate, and TP valves need replacement now and then.
It is not recommended by water heater manufactures to use 150 psi TP valve when water heater came with 125 psi. Rating shows in small print on end of TP. New TP valves sold at local hardware. Let tank cool before installing new one.

7) Higher temperature and high pressure can rupture tank.
Pressure over 80 psi shortens life of water heaters and plumbing fixtures. Put BTG100 pressure gauge on water heater drain valve to check pressure.

8) You need a drip pan with 3/4" drain line to outdoors, or to drain vent line, to prevent flood caused by ruptured water heater.
Turn water heater off when going on vacation.
Inspect water heater each 6 months.
Drip pan available at local home center or hardware:
http://waterheatertimer.org/9-ways-to-save-with-water-heater.html#drip

9) Heated water expands and puts pressure on tank and pipes.
Water does not compress... so when water gets hotter it expands against tank wall and against pipes.
Especially in closed system (check valve present) when system is without expansion tank.
Expansion tank is installed on incoming cold water line.
http://waterheatertimer.org/9-ways-to-save-with-water-heater.html#expansion

If you need further help, I’m available over the phone at https://www.6ya.com/expert/gene_9f0ef4df2f9897e7

That will depend on how much is exposed to conditions/weather, that caused it to freeze. A good place to start is to heat valve and and piping that you suspect is frozen, with a hair dryer, or heat gun, if possible. Try to move it along entire area, rather than concentrate on one spot. Where it's located obviously will have a bearing on how you do it as well. Can you give a little description of how much pipe, etc., that you suspect is frozen, and where it located, as in access wise?

If this is an electric unit, you have to remove the cover to locate the thermostat. It sounds like the thermostat is malfunctioning. The excessive hot water can cause a unit to leak due to the expansion of the unit due to the overly hot water. Make sure that your breaker is off before you remove the covers to expose the thermostat.

Someone has not sized the system correctly. The water heater will heat a certain GPM a certain temperature rise. Most of those "generalizations" from the manufacturers are referencing the lowest of all the flow requirements like 2 lavatories. The truth is, don't use other fixtures while showering or get a bigger system. Lots of information related to sizing the tankless system at http://www.mechanicalengineeronline.com/Mini_Sites/Tankless_Water_Heaters_Ebook/Tankless_Water_Heaters.htm Have a good one. PS:Properly sized On-Demand water heaters are actually really good. Be prepared for the day your water heater quits.