If your water system has a check valve or anti siphon valve on the supply line an expansion tank near the cold intake to the heater will likely be necessary.
Adding a tank to a tankless water heater.
A tankless heater in series with your tank should work but i would consider two alternatives.
How to switch from propane tank water heater to electric tankless water heaters.
According to homeadvisor the average cost of a 40 to 50 gallon tank style water heater including installation is 889.
I also made a video so you could see our install first hand.
Before the slug of cold water from the tankless heater reaches the showerhead it mixes with the hot water in the small tank preventing the icy blast.
A buy a bigger water heater.
See the heater owner s manual for more information.
If a tankless water heater is being used in conjunction with a tank water heater or a recirculating system that utilizes a storage tank in a closed plumbing system an expansion tank is required to control thermal expansion.
The average cost of a tankless water heater including installation is 3 000.
Like the tankless option it would only draw significant power when you draw down the main tank.
So here is my feasibility question.
A well insulated extra storage tank in series with your main tank.
Disadvantages of tankless water heaters.
Tankless units are more expensive.
Tie in new hot and cold water lines to the existing water lines with copper pipe and run the lines to the new water heater.
By locating the small tank in a closet or under a vanity in a bathroom you can enjoy the convenience of instant hot water with the efficiency of the tankless water heater.
This does not apply directly to most homeowners who have a tankless water heater system.
Best of all tankless water heaters are energy efficient because they don t heat water when it s not being used.
Switching to tankless water heaters isn t that hard.
Here are the steps we took to convert from a propane powered water heater to an electric tankless water heater.
An electric tankless unit will cost about 500 to 700 roughly the same as a traditional tank model while the cost of a gas tankless heater runs about 1 000 to.
I would prefer to not use option a as the only time that much hot water would be used is for a bath and that seems like a waste of electricity to me.
This article includes a sidebar comparing details of tank and tankless water heaters.