Adding Storage Tank to Gas Water Heater

[RockRiverShooter]

Hello All -

I am adding a storage tank to my new 75gal gas water heater setup. I plan on using a (non-electrified) 50 gal electric as my storage tank.

A few questions:

What is the optimal piping configuration for this setup?
Correct size (flow rate) of circulating pump should I use?

My initial plan is to feed cold water into the 75gal gas tank. The hot water outlet will feed into the cold water inlet of the 50gal storage tank and then the hot outlet of that tank will feed the house fixtures. Seems pretty straight forward, but am unsure on best way to route the circulator pump.

My plan is to use a brass Taco pump 003 or 006 and hook it up to the lower thermostat of the 50 gal tank. This way it will activate the pump to circulate when the storage tank is below temp at the lower thermostat. Will shut off pump when the storage tank is at set temperature so the pump does not circulate 24/7.

I have unused side ports on the 75 gal gas tank, and tee's on the drain valves on the bottom of both tanks. How should I route the circulation between the two tanks? The Taco pump has an integral flow check so no need for a separate check valve between the tanks. No pressure reducing valve installed or check valve on the city meter so no expansion tank required.

Appreciate any advice. Thank You! Pics and diagrams welcomed.

 

[John Gayewski]

The pump would go on the drain of the electric storage tank up to the inlet of the main heater. Those integral check valves are junk. Most of the time I take them out and use a regular check valve. You'll want pump isolation valves. The 003 is plenty more than you need but it's the smallest available. I'm not sure on your wiring I think you'll obviously have to disable the elements but I'm not sure how the thermostat will work with them disabled. Lemme know how it goes. It's an interesting idea.

 

[Sponsor]

 

[Reach4]

If you run power to the electric WH, you could use that as a backup in the case of a gas water heater failure to heat. If you put in valves, you could even use the electric as a backup in the case of a gas WH leak until you get the gas WH swapped out. Or you could use both WHs in series for some special event where your showers are going non-stop for a while.

Given how reliable gas supply is, having a backup for that seems pretty useless.

If you open the breaker to the electric WH, or set the thermostat way low/off, it will not be turning on in normal operation. I suspect your plan was to not run power at all if it is just storage and not a backup.

 

[Fitter30]

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[Fitter30]

 

[Master Plumber Mark]

Its a great idea you have ,,,
but you might be better off to let the 50 gallon heater just be the first that gets
water inside it and let the water come up to room temperature and then go into the 75 gallon unit
that feeds the home ...

If you take the jacket and insulation off the 50 gal tank it will come up to room temp
over an hour or two and then it would feed the 75 heater...

you would do this in series and I have seen this before , it is a passive way to capture heat from
the home to do the standby heater


another option would be getting a 50 gallon electric heater and just installing a 110 volt element
into the bottom opening.... plug it into 110 v with and just set the T-stat it on low.... then make it the first unit
going into the 75 in series..