"That damage is not related to which runs more but rather how they're vented/when it begins drafting."

A Seattle-area homeowner's estimate of $2,500 per unit to replace two 15-year-old water heaters sparked a lengthy debate on Reddit's r/AskAPlumber forum.

What the estimate included

In the Reddit post, the homeowner said the plumber's proposal bundled several repairs together, including repiping older CPVC in the mechanical room, fixing a stuck backflow device, replacing a failed expansion tank, and addressing corroded copper supply lines.

The two water heaters alone were priced at $5,000.

The original poster also shared an image of the estimate and said there was "Some age/heat related damage to one of the tanks. [The] other is fine." The homeowner added, "That heat damage is the only real sign of problems. No signs of leaks anywhere."

Reaction to the price was divided. One commenter said it was "about normal for our neck of the woods," while another plumber replied, "I'd charge considerably more..."

The most practical advice centered on comparison shopping. One user wrote, "Get 2 more quotes. It's a big job. Not an emergency. Getting 3 quotes lets you compare pricing and get a feel for each company over there."

Another part of the discussion focused on the home's plumbing layout. The house uses two 50-gallon water heaters connected in parallel, and the homeowner said the plumber explained that this setup "usually means one runs preferentially over the other."

That explanation was challenged by another commenter, who wrote, "That damage is not related to which runs more but rather how they're vented/when it begins drafting." The same commenter said parallel heaters "pull from each equally," suggesting the visible damage points more toward a venting issue than uneven use.

One commenter said the estimate made more sense once it was clear it covered two units, but still questioned why anyone would install two 50-gallon gas heaters in the first place. Instead of replacing the system in the same configuration, the commenter suggested BW Aerotherm heat pump water heaters, saying they offer "more capacity and cost less to operate."

Keeping the duplicated setup simply because it's already there can add thousands of dollars to a replacement project.

For homeowners weighing alternatives, Cala offers a different option from swapping old gas tanks one for one. Cala's customizable smart heat pump water heaters are designed to heat water only when needed, which can help lower energy bills. For a home facing a $2,500-per-tank quote, that level of efficiency may matter as much as the labor cost.

Before approving a like-for-like replacement, a homeowner may want to ask whether the house still needs two tanks and whether gas remains the best choice. For homeowners already reconsidering an aging system, Cala is one example of a replacement built around actual hot-water demand.

Where can I learn more?

Here are a few related stories about two-tank systems, replacement quotes, and whether sticking with gas still makes sense.

• A homeowner with two 50-gallon water heaters wondered whether shutting one off would reduce standby losses.

• A homeowner asking whether two water heaters were plumbed correctly learned that replacement could mean opening walls.

• Adding a second water heater left one homeowner with 80 gallons of lukewarm water.