Hi Maliha,

With 7 people - you for sure need as much as you can get. Short answer - if you can get someone to guarantee the install and get you thru any inspections - you won't regret it.

However, your description is throwing up some flags. This isn't really a 'designer's' questions as much as it is an engineer's & here's why I say that (risking my profile to the angry designers out there)

1) How did you end up with a giant commercial WH in the first place? What was going on that made someone put that in? Codes? Covering up another problem? It's obviously OVER designed.

2) 50k vs. 200k BTU - that's quite the load change on your electrical panels & may require some change. Also makes me hope the current utility set up is tuned & not just jerry-rigged in a way to work, and not meet code.

3) As you state, you have this circulation system built around what's there - is that even to code or did someone just install this giant system for their own 7 person need?

4) If you go smaller, you have a honda engine in a ferrari... if you stay the same you may have a ferrari with a bad transmission. (Sorry, I'm from NYC, don't drive, but hope those make sense)

Sorry if that's a little information overload. It's why we give every project a 15 minute evaluation, totally free. Hit us up.

Thanks,

-f

200,000 BTU is probably gas, not electric.

"We have huge blasting showers in master bedroom."

Proper mechanical infrastructure is required to support such luxuries ... along with the cost involved.

Get rid of the water wasting shower and the $300 a month water and gas bill will go away. With piping that can support 199KBTU, you have an easy conversion to tankless. You’ll need to address the different venting needs, but you’ll be all set for the next 25 years with tankless.

Have an on-site consult by a commercial plumbing company. There are many things that factor into correct sizing for HW delivery; length of piping runs, whether those runs are in a climate controlled space, your geographic location and your specific type of circulation system (continuous or on-demand).

firstly , thanks for all the answers!

we bought this house last year and it was built in 1983, the owner was a commercial builder himself and he built his house like a solid fort! We did consult the plumbing company that always worked for him, and the plumber came yesterday and basically said we have both options , to go with residential or commercial. He will have to cut around the pipes etc . However he strongly recommended against tankless when my husband asked him about it. If he even did that, he would have to put holes in ceilings etc and we don’t want that.

i dont want to get rid of my showerhead .. ! for years I had an ordinary shower and now that I am used to this, can’t go back. I don’t care about $300 bill.

As for proper mechanicals and stuff, When we bought the house there were inspections and as such there was no issue if anything was done improperly . In fact, everything has been laid out quite transparently and evdn the wiring is so organized ( basement is unfinished which I don’t like aesthetically however my husband says that’s the best part . You can see what and where everything is, especially when something goes wrong .

So i just wanted an idea if anyone here has a residential water heater like 75 gallon or two heaters and if they run into problem with hot water . I only have one comparison and that’s from my old house which was a meek 50 gallon and was sorely insufficient. I don’t know how it would be if it was something in between the small 50 gallon and the huge commercial one we have now Along with a 120 gallon storage tank.

The plumbing company guy said this commercial they install in apartment buildings and said it’s an overkill for this house, however he did say that if people were to take showers back to back, kids in bath tubs, Potentially residential would fall low .

If you like the system you have now and are not worried about the $300/mo., why worry about the $7500? At least that way you’ll have peace of mind.

If you intend to stay with this plumbing company that installed and services this system, you might want to take his advice.

IMO

SR

Recirculating for instant hot water is a different system that will stay regardless of what we install.

Lolll.. true your comments.. however the main reason I did the jump from a 3200 sq foot home to a 6500 was because 4 kids were sharing one bathroom then and I didn’t want them waiting to take showers!

I am doing a remodel. Get the replacement for what you have now - get what you love and makes your life better. Anytime I went for a cheaper option of something I really wanted, I regretted it. My bathroom floor was 5x what a normal tile was and it made me question my sensibilities but I LOVE IT and have no regrets now that its in and paid for. When it’s bedtime and your kids need a bath or when you and your family have a special place to go one day, waiting for hot water is going to suck and you are going to kick yourself for not spending the $5k.

Agreed! My husband always says the same thing go for the v best you can afford. With this however is a bit reluctant because of the price and feels that we may never really need it. he has left it up to me . We have to decide quickly too we don’t want the leak to keep increasing. My husband is doing wet vac twice a day.

I agree but only if I can find out how the one residential 75 gallon along with the storage tank would work and maybe that would be more than enough for us and we may never run out even if we take 8 showers back to back.

okay - I think what you have to do is see how many gallons per minute your high powered showerhead takes and add that up with how long you use that shower. A 10 min shower w a standard head uses 25 gallons. Then see how many gallons your tub holds (count about 1/2 that bc you only fill it up that much normally) and how often baths are taken. You also have to account for laundry & dishwasher too. So combine all of those for the busiest 1 hour period and see if your tanks will handle it. Also check out the rapid reheat models.

mandy has the right idea, you should be able to figure out yourself, or your plumber can help to check. Personally I'd be surprised if the smaller model wasn't sufficient. I think the way to understand it is this: the water heater's size determines how quickly you can replenish the storage tank (or recover from all the water being used), and - at the margin - continuously heat. The storage tank's size drives how much hot water you can use in a short period before running out.

Bottom line is basically, how many of your seven people take a shower in a short period of time? Does everyone expect to have a shower within a single hour in the morning? On paper, your 120 gallon tank would cover 4-5 standard showers, likely less than that in practice with other needs (handwashing, kitchen usage, etc).

The 50k BTU heater should have a figure for recovery in gallons per hour - perhaps something like 50. That's basically its maximum output. It would then take two or three hours to heat up your large storage tank (whereas your current 200k unit would fully recover in an hour). The hot water heater itself will have storage (50 gallons?) to include in your calcs.

It sounds like your current set-up is more or less sized to be able to meet maximum likely demand at all times, with no significant recovery period - i.e. it might be able to meet all demand without the storage tank just by running the heater. Of course, keep in mind there are losses in the system and the real world 'hot water at the tap' will be somewhat lower.

So you should be able to figure out how to test this. But fairly simple logic test - if everyone takes showers at different times of day, likely no problem. Even spread out over 2-3 hours you may be fine. If everyone takes two extra-long showers a day and all within the same time periods, maybe not.

A few additional thoughts:

-Of course, keep in mind laundry and dishwashing needs. But also check if they even use household hot water - mine do not, they heat water internally. (Then considerations of when you run them, of course).

-Have the plumber check the storage tank - it'd be a shame if it started having problems right after, and they're likely the same age.

Also note, assuming this is gas-fired, it's not a bad thing to have a smaller one running for longer periods. (I'm also a bit surprised there are only two sizes available - surely there are in-between sizes available, like 75k or 100k BTU?)

I'm in a seven person household, too - and in my experience it's rare that everyone takes showers within short periods. I can't compare my set-up (household heat and hot water from same boiler), but on paper I wouldn't think the extra expense worth it, just based on our actual usage. Of course, if you're the last person to shower after everyone else and you can't stand even once running out, you might think differently.

We are a 5 person household and haven't had any problems with 2 x 40gal residential water heaters in series in one house and 1 x 80gal water heater in the other house. Admittedly a little smaller than your clan. 2 x 75 gal heaters in series should be way more than you would ever need,

Steer clear of tankless for your situation.

Armoured is telling you what you need to know. A residential 75 gallon will be just about the same size as an 80 gallon commercial. The difference will be the recovery time, that is, how long it takes to reheat the water coming in. The residential one will be longer than the commercial one due to the size of the burners (the BTUs they put out). Remember that you have a total capacity of 200 gallons (both tanks)

Do ALL the showers in the house have 'big blasting' shower heads or just the master? If they are otherwise 'normal', then my guess would be that you won't see any difference between 195 gallons and 200.

BTW: This system wouldn't happen to be supplying hot water for hydronic heating, would it?

A 199K BTU tankless can handle 117 showers one after the other, not just 7. All without ever running out of hot water.

So here's the thing: nobody here can answer your questions without knowing what the actual hot water demand is (and big blasting showerheads gives us an idea it's more than 2.5 gpm... but we don't have actual numbers to work with).

This kind of gluttony and waste just makes me sick - but the real answer to your question is that this is an engineering problem and we don't have the facts. Anything we say is wild guessing.

A few observations... from the pictures you provided it looks like you have 1 commercial grade water heater, with an additional holding tank for hot water produced. (There's no flue coming off the second tank, which would make this a holding tank.)

There is a circulatory pump toward the base, that's a requirement to make this system work. (design of the system)

The pipes going into the water heater are 1 inch same as the holding tank. (This is important in terms of flow rate. All residential type water heaters are 3/4 inch.)

If you cut down water flow due to size of the pipe (leaving & returning), this can effect capacity of the hot water... meaning you could have plenty of hot water in the tank, but it's not getting to where it needs to go fast enough... the flow of the pipe size creates a bottle neck.

The flow of water in a 1 inch pipe is far greater than that of a 3/4 inch pipe.

Just to update: we went with a residential 74 gallon water heater .. total cost including installation was about 1600. So far we have not noticed any difference. That along with a 120 gallon storage tank that we kept as it was, I think we are going to do ok.

if we do run into problems then we would get a second residential in parallel

Maliha, thanks. I find here that one of the most useful things is when people update on their real world experience, which doesn't always happen. It is really helpful to other so let us know. In your case it sounds like the cheaper solution is fine in real world usage. Congrats.