Tankless are best close to where you use them and often you need more than one with 6 showers

Is the current hot water heater gas or electric?

Was just about to answer - it’s gas.

Tankless water heaters are rated in gallons per minute. If you are running 5 shower heads and each is using 2 gallons of hot water per minute, then you need at least a flow rate of 10 gallons per minute. The Rheem Performance Platinum 11 GPM Natural Gas would probably be able to do it, then there would be little excess capacity for any other faucet or appliance. In addition you will have to upgrade the gas piping to the hot water heater. It can become an expensive installation cost.

How many people in the house and how many showers are taken at the same time? I am skeptical you even need another 75 gallon hot water heater.

The shower heads are 2.5 so 5 would 12.5 GPM. I can’t find one that will handle that in a north east climate where ground water temp can be low. In terms of tank - When we used to have a 50 we would run out of hot water if dishwasher plus bath for example (shower wasn’t built yet). May have been cause tank was old but did not happen with 75 gallon.

You can go tankless BUT, it will require several units "run in series" to meet your needs - $$$ - and they DO require maintenance. Better to invest in a new plumbing configuration and two Marathon tanks by Rheem. These are "blown" tanks (no metal - therefore they cannot rust) and come with a Lifetime Guarantee to the original purchaser.

What would a better plumbing configuration look like? Right now there is one water heater for the whole house. It’s in the basement which has a low ceiling so it’s tough to get it too high off the floor. The 6 or 7 inches of water that overwhelmed the sump was enough to wipe it out. I don’t really need to go tankless -our hvac person just asked and I told him I didn’t think it possible based on what I’d seen. Interested in how you’d reconfigure. Are you thinking 2 40 gallons?

In your shoes, I would replace like with like. You'll pay a fortune to have a tankless system to provide the flow you need.

In my area, Bradford White is a respected brand. I have two of them. If there are many homes in your town and neighborhood needing to deal with the same problem, you may be stuck getting what's available. But hopefully distributors will be able to shift stocks from nearby areas to the affected flooded areas to make more products available.

Good luck.

Marathon heaters are electric...BONUS...no need for a vent flue. Because they are not made of metal, any flooding will have no impact on them. Your Plumbing Pro will work out a new piping plan, making sure that every "point of use" will have sufficient flow, and select the size of the tanks needed. These tanks are available in "short" versions if needed. Then your Electrician will run the wiring. Rather than sitting on the floor, I suggest setting them on concrete blocks, as this makes the yearly draining (which no one seems to do) much easier.

Electric water heaters can be considerably more expensive to operate and much slower to recover from use (producing hot water from cold water) than gas heaters. The expense of having an electrician install higher power wires to the install site is an additional cost that is avoided when installing like for like.

Chili - Electricity is much more expensive than gas here. Not really looking to switch .. . Is there a gas equivalent? My hvac person doesn’t seem terribly interested in my house’s plumbing in general. Just what he needs for furnace and hot water heater. Elmer - I’m hoping we luck out due to large tank size. If we were looking at 50 we might be in trouble.

Yes, KD, could be. But if there are supply shortages, someone who might have wanted a 50 gal size could opt for the 75 if that's what's available.

Hopefully you can get your need filled. Sorry for your trouble, we have some friends living just a tad north of NYC whose basement flooded and they said both their HVAC and water heating equipment need to be replaced, apparently.

Water heaters have been hard to get in our market. You might need to be flexible to get something installed in the near term--even if it's just on a temporary basis.

Thank you - we'll see what's out there in terms of replacement. We had our furnace checked and so far it seems we were lucky in that regard. That said, unlike our water heater which is only 5 years old, our furnace is pretty close to end of life anyway so if it's impaired when we fire it up in the fall it'll hurt less.

Have you tried locating a gas-fired 75 gallon commercial tank? Commercial tanks are more expensive but, might be more available. Ruud makes a "short version" - 60 inches tall.

How high was the water in the basement? Was this fresh water?

Chiflipper - we are waiting on our hvac person to report on availability. Mike - Water was about 6” high. It was rain water.

Given that this is an expensive hot water heater, that is only 5 years old, and it had 6 inches of fresh water, you could consider repairing it. The gas burner assembly would have to be removed, dried, and cleaned. The key part is detaching the gas tubing to the pilot. There is a small orifice that has to be cleaned. You also have to dry out the water at the bottom of the tank and make sure the air input screen is not clogged with debris.

The problem is finding someone willing to do this repair properly. It would be worth calling the manufacturer for information on a authorized repair company.

Yes, I second that you need to just replace with a similar unit. Tankless would require a re-design and would be very expensive. You do have an alternative with a condensing tank water heater which would give you many of the benefits of a tankless - but without most of the issues.

A Marathon water heater ONLY makes sense when electric resistance heat is appropriate. Electric resistance heat is usually the most expensive way to heat water.

Looks as though we'll do like for like. HVAC person called and there is exactly one standard 75 gallon unit at the major distributors and it's ours now. Thanks everyone! BTW HVAC person concurred that tankless wasn't the way to go. And we are in a little bit of a "take what's available" situation right now given Ida.

Sounds like a very good outcome under the circumstances. Good luck.

I am curious why anyone wants 6 outlets in a shower…?…

It’s 6 outlets in one shower. 3 body sprays in wall. One overhead rain shower (gentle). One regular strong shower head. One handheld. It’s really not that extreme. We also have another bathroom with 2 outlets.

Usually body sprays are 1 gpm each - but yeah... it's pretty over the top.

"That's 10-12.5 gallons per minute - Your 75 gallon heater can't keep up with that."

If that's the flow rate, and the mix is half hot and half cold, let's say it would be 5.5 gallons per minute of hot water. If all were on, a 75 gallon tank could probably last for 15 minutes plus some because the burner will come on right away so that the existing water in the tank will get hotter and the cold water being added will warm up.

In my state, shower heads are limited to something like 1.8 gpm and for showers with more than one head, I think the limit applies overall.

Lower flow showerheads work fine, they typically have a narrower stream and the water passing through is accelerated to come out harder, to feel more brisk. Water doesn't trickle out by any means.

Stay - 75 gallon has no problems keeping up. No need for name calling. And we’re fine running other appliances. Jake - The body sprays are Kohler water tiles at 2.5 gpm. That’s the default here. In my next bathroom I am going to try harder to get some lower numbers. You all make me smile a bit because we toned this down from the 5 body sprays the designers suggested as standard. Anyway It runs through the Koehler digital control system so we can voice command it. Now the Toto neorest toilet is arguably over the top and the ikea networked shades …. Lol. It’s really been great during covid though.

I think it is irresponsible to use that much water…if not illegal