Defiantly a plumber but are you certain tank isn't sitting in a pan? Code normally requires pans beneath second story tanks,esp if downstairs is a different owner.

If it's more than 5 years old you can count on plumber recommending replacement.

Thank you, I don’t recall a pan underneath, and yes it’s way older than 5 years! I guess it would be good to research how water heaters work, but I assume it would damage the unit below if it emptied out. I don’t know how much water it actually holds.

Since you aren't familiar with how water heaters function I understand why it might be causing you to worry. Let's consider some facts and perhaps we can set your mind at ease.

(A) Most important consideration is whether unit below is permanent residence, week-end resort or like yours, annual resort. This let's us know how soon a leak would be noticed due to water dripping from ceiling.

(B) Share your concern with your insurance agent to see if damages would be covered in such an event. NOTE It is not requisite that you as the insured make judgements on fitness of the water heater so don't speculate.

(C) You might find comfort in knowing that I've never known a heater tank to fail and begin leaking while not under water pressure. As a side note, it is very common for drain valve to drip when restoring pressure after a long period of dormancy. That is to say when you go for a stay, glance at drain valve a few hours after turning water on.

Hot water heaters will usually have the date of manufacture on a plate on the front of the unit. This will give you an idea how old it is. A hot water heater typically lasts 10 - 15 years. You can buy a leak detector alarm if you are concerned about property damage. There are types which can be be connected to WiFi. The alarm can be sent to your smart phone for times when you are not present. If a pan was installed, it may connected to a drain line. If a gravity drain is not possible, then ask the plumber about connecting a condensate pump to pump to water to a nearby drain.

You are the perfect candidate to replace that old heater with a tankless model. You have warm incoming water temperatures, and are gone for long periods. A tankless will only make hot water when you turn on the faucet.

@Minardi

Re: Tankless

They have an electric water heater now - and I never recommend electric whole-house water heaters. They are also in an older condo - so no ability to upgrade the electrical service that would be needed by an electric tankless heater. For those reasons, a tankless isn't a good idea.

A tank heater has a very low likelihood of "opening up" when not under any pressure. That said, a metal tank heater that's 10 years old or more would be a good candidate for replacement in this situation - just for peace of mind.

I would recommend a Rheem Marathon fiberglass electric tank heater. That way you don't have the concern of it rusting through. A proper pan is not only code, but would further reduce the likelihood of a minor drip from a drain valve, for example, causing trouble.

In general, electric resistance water heaters are the most expensive way to heat water - and I'd normally be looking at the possibility of using a hybrid electric. But the fact that this isn't occupied for long periods of time - and the need for assurance that the tank is durable - means that the Marathon heater would be my choice.

And remember to turn off power to the heater whenever you turn off the water that supply it. If the elements are not immersed in water, they will burn out almost immediately. I would also think about replacing the heater for peace of mind.