1-of-2 water heaters is busted, can I still use the other?

[BrianFtx]

BrianFtxNew Member
Hi all,

DIY guy here. Two Gas water heaters installed right next to each other at same height (one in a closet, the other just outside the closet).

One was replaced this past summer (New), the other is 15yo old (Old) started leaking last night, then the entire drain valve completely broke off the tank. I'm not sure how they are plumbed, and not sure what is safe to do here. The New heater has a shut off on only one line (I'm assuming in inlet line). The Old heater has shut off valves on both lines.

Currently I have turned off the gas to both heaters, and both lines on the Old heater are shut off. The Old tank is empty. Both lines on the New tank are open. With this set up, I still get water coming from hot water tap, it's just no longer hot.

My question is this: can I restore gas/heat to the New heater and have hot water supply for the house while the Old heater is completely shut off & turned off?

My thought is that, if they were plumbed in series, then shutting both valves on the Old heater as I have done would stop water from coming out of tap when hot side tap turned on. Unless the New tank is the second tank in the series and it is somehow drawing water from the new tank outlet despite the fact that there is no new supply coming into it. Seems like shutting both valves on either tank would stop hot water from making it to a tap's hot side. So since I have water (even though it is cool water since all gas is off) coming out when I open hot tap, is that proof that these are plumbed in parallel??

This leads me to believe they are parallel, which hopefully means I can relight pilot and restore gas/heat to the new heater while the old heater is completely shut off, allowing me to have hot water until the Old tank is replaced.

Does this make sense?

Thanks for any thoughts/advice!!

 

[Geofd]

shut off the gas to the old heater shut off the hot and cold....CAP OFF THE GAS FLU TO THE OLD ONE....then see what happens while running just one

 

[BrianFtx]

How do I go about capping off gas flu to the old one??

 

[Geofd]

How do I go about capping off gas flu to the old one??

are you going to replace the old one???? if so just remove the flu from the water heater get the the appropriate cap size...screw it to the exsisting flu if you not going to replace it go back to the branch fitting on the flu and cap there and remove gas and water piping

 

[BrianFtx]

How do I go about capping off gas flu to the old one??

...and why do I cap it off if it's not on?

 

[BrianFtx]

Yes going to replace in a week

 

[Geofd]

...and why do I cap it off if it's not on?

because its still connected to an active chimney or flu..... if you are asking these questions you should leave this up to a lic/insured plumber.....
that's the best advice you should take today....don't fool around with gas!!!!!!!!!! shutting off water valves is one thing.....my fault for giving you advice.....call a plumber

 

[BrianFtx]

Is capping the flu on the old one that is shut down necessary for safety?
I'd like to have hot water for the next week, but not sure I can successfully cap this, and I don't want an unsafe scenario

 

[BrianFtx]

Yep, that's my plan. Leaving gas off to both until a pro gets here

 

[Geofd]

PLEASE CALL A LIC/INSURED PLUMBER YES ITS A SAFTEY ISSUE DONT FOOL AROUND WITH GAS!!!!!!!!!!!!!!!!!

 

[Geofd]

Yep, that's my plan. Leaving gas off to both until a pro gets here

you made the right call.....

 

[ExtraMilePlumbing]

Is capping the flu on the old one that is shut down necessary for safety?
I'd like to have hot water for the next week, but not sure I can successfully cap this, and I don't want an unsafe scenario

I believe due to chance of a backdraft from either plugged vent or a power vented appliance pushion co2 down