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Supplying Hot Water To 4 Apartments

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Old 03-29-2009, 09:11 PM   #1
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Supplying Hot Water To 4 Apartments

Hi guys,

I'm normally on this website reading the landscaping, paving, and site work forums, (which are my specialty), but currently have a plumbing question that I'm hoping you guys can help with.

I purchased a foreclosed property to rehab. It has (1) store front which is occupied by a doctor, and (4) 1BR apartments that are vacant. There is currently only a single 40 or 50 gallon electric powered hot water heater to supply hot water to ALL 4 apartments. (The doctor's office has it's own hot water heater). I already know this is going to be a problem, and have no idea how it was working in the past when the building was fully occupied. For a quick test, I turned on 2 of the showers at full blast on hot water and the hot water only lasted for maybe 8 minutes.

I have a pretty good contractor doing the majority of the rehab work, and his friend who is helping him has a decent amount of experience with plumbing because he used to work for one full time. There recommendation is to install an 80 gallon hot water heater next to the existing one, plumb them together so they are constantly circulating the hot water, and go with that. They did state that gas would be more efficient, but we then have to worry about installing a flue (sp?), which they said will be a challenge on this particular building. They are also trying to recommend something that will not cost an arm and a leg.

My questions to you guys is this:
Will the 80 gallon plus the 40 gallon provide enough hot water for (4) 1BR apartments? Some apartments may have a 2 people living in them. Could hypothetically be (8) showers.

Is it ok to hook (2) hot water heaters together and have them circulate the water?

Could we use the doctor's hot water heater to help heat at least one or two of the apartments, or also tie his into the 2 heaters specifically for the apartments? (His hot water heater is located about 15' away from the other hot water heaters in the basement.)

I was looking at tankless systems, but it looks like that would be in the $10,000 range, which is more than I am looking to spend right now.

Sorry for the long post, and thanks in advance for any help you can provide.
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Old 03-29-2009, 10:08 PM   #2
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Re: Supplying Hot Water To 4 Apartments

A plumber would know about
high efficiency gas heaters
that don't require a conventional
flue, but use a horizontal PVC vent.


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Old 03-29-2009, 10:23 PM   #3
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Re: Supplying Hot Water To 4 Apartments

AO Smith has a really nice document for calculating the water heater BTU and gallon storage requirement for apartment buildings:

After you calculate the water heating requirements with this document:

Then you need to pick one of their water heaters from the 3-hour sizing chart:

It's a little bit involved, but very interesting. They also have an "accu size" program that you can download: I don't like it as much.
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Old 03-29-2009, 10:30 PM   #4
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Re: Supplying Hot Water To 4 Apartments

Why would a tankless system cost you $ 10k? That seems pretty excessive.

Without pulling out the Rinnai books I'm thinking you could get away with 2 of them running in parallel, all power vented to the outside for 1/2 that, provided the gas main is nearby since they are heavy gas users (200k BTU) needing a bigger dedicated line from what I have seen.

If you have the chance to use gas, use gas for price savings and faster recovery of hot water in a tank situation
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Old 03-29-2009, 10:45 PM   #5
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Re: Supplying Hot Water To 4 Apartments

A water heater in each unit would be the way to go - any other way & good luck, especially when they find out it is on a shared system. It shouldn't be that expensive, less water waste (run from heater to kitchen & bath), if 1 heater goes down, only 1 tenant is hollering - not 4, etc... Just my .02

PS - don't screw with the doctors HW supply, there is a reason his is separate & you need a licensed plumber as I recall in PA (unless your doing the work by yourself?)
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Old 03-29-2009, 11:42 PM   #6
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Re: Supplying Hot Water To 4 Apartments

There is currently only a single 40 or 50 gallon electric powered hot water heater
Why would you want to heat the water if it's already hot? That aside, I'd stick an electric in each unit and let them pay the heating bill. I assume they have separate power meters.
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Old 03-30-2009, 12:50 AM   #7
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Re: Supplying Hot Water To 4 Apartments

I say replace the current one with a 80 slap in another 80 and your good to go. These are one bedrooms apartments so that should cover it . But i also like Chris Johnson ideal going tankless. I also don't see how that guy gets 10,000 for tankless. In my town there are business with apartments above. My plumber owns one of those. 6 units at 500 a month above his shop. Thats a nice way to supplement your income.
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Old 03-30-2009, 07:16 AM   #8
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Re: Supplying Hot Water To 4 Apartments

Originally Posted by SLSTech View Post
A water heater in each unit would be the way to go
Agreed. Higher initial investment, but much better to have each tenant paying for his own usage.

you need a licensed plumber as I recall in PA
There's no state requirement, but the larger cities generally require one.
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Old 03-30-2009, 07:18 AM   #9
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Re: Supplying Hot Water To 4 Apartments

I'd bet dollars to donuts the building is on one meter. Very few older apartment complexes are seperately metered.



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