One hot water heater for 32 Units... enough?

Question

I wish I posted here more... but I do spend a few minutes each night perusing.

Here’s what I’ve got:

Purchased a 32 unit former motel property that will now be 1/1 apartments. Kitchen sink, bathroom sink, tub/shower.

There is 1, (I believe) 100 gallon GAS hot water heater servicing the entire building. It was 50% occupied when I bought it 4 weeks ago, now 65% occupied and no HW complaints yet.

Is this one unit (probably) going to be enough to service 32 apartments?

If it isn’t, would using a HW storage tank connected to the heater be effective vs. adding/daisy chaining a second?

Thanks in advance!

Kerroll Barnes · Answer

@Steve Stuart

I’m a plumber from NY and there is no way 100 gallon will suffice such a big building.

The best thing to do is contact your local plumbing supply and they will be able to assist you in what size tankless instant hot water heater to get.

I have a 2 family and I went with a combi boiler. Hot water and heat together.

Also check to see if you do have the little heaters under the sink or in the ceilings that heats up the water.

Randall Alan · Answer

So believe it or not... there's an app for that... albeit on the web:

http://www.hotwatersizing.com/...

Super simple and specifically targeted at hotels / motels.  A lot depends on the temperature rise of your cold water source.  But check it out and let us know.

From what I played with, it looks like a 120 gallon tank could do it... but it does all the calculations for you.

Totally blown away that could possibly work, but according to the calculator it could!

All the best!

Randy

Steve Stuart · Answer

Thank you all for the responses. This is a tank in the mechanical room. There’s a 1,000 pound safe next to it (had it cracked last week, empty) which has obviously been there for years (decades?) so doubtful there has ever been another tank.

There are no on demand/electric systems in the units.. just this gas tank feeding the entire building.

It’s definitely a commercial heater which I don’t think could be compared to our residential HW heater (correct me if I’m wrong?).

Matthew Paul · Answer

Its possible , it depends on the firing rate of the heater . It would have to be oil or gas , electric wouldnt recover fast enough .

Randall Alan · Answer

I'm really confused... How can 100 gallons be enough for that many units?  My bet is that they have instant hot water units in each unit?  They can be really little... sometimes under the sink.  I wouldn't think that a 100 gallon unit would be able to adequately service 4 units, much less 32.  Something doesn't sound right.  Heck, it could take 20 gallons of water just to heat up the pipes to get the hot water to unit number 32!

Think about 7:30am... 20 people trying to take a shower to get ready to go to work.  100 gallons 'ain't' going to cut it, be it a gas unit or not!  Sure you aren't missing something?  I would look around for other sources of heat, like the tankless heaters.  I was at the beach near me and they had these mounted outside each unit... so doesn't necessarily have to be inside.  They look like a box hung on the wall with water pipes going in and out.

Randy.

Jonathan G. · Answer

@Steve Stuart

Sounds incorrect.  Please revisit the property/ system and update the group.  Perhaps it’s a larger on-demand unit .  I have 2 fifty gallons in my own personal home and have run out of hot water on rare occasions so it’s not likely that the current/complete understanding of your system (as you described it) is accurate.

Randall Alan · Answer

Sorry Jill, after re-reading I see that... cheers!  And I think a large on demand system with a hundred gallon holding tank the other person mentioned makes sense to me... bet you that is what it is.

randy

Justin V. · Answer

@Steve Stuart

You have to be missing a lot if it’s a “tank” and not an on-demand system. Call out a plumber so you can understand your system or what did your inspector say?

I have a 10 gal/minute on demand system for my house which I believe is designed to handle 4 or 5 showers at once, so if you have a 100 gal/minute on-demand system that will meet your load. I’m currently assuming you are misspeaking “tank” instead of “on-demand”. I’m going to also guess code wouldn’t allow them to have less hot water than needed for 100% occupancy, but I’m not into anything bigger than a 4-plex, so I’m just making assumptions.

Joe Splitrock · Answer

@Steve Stuart you need about 10 gallons per occupant if it is a gas tank water heater.I had a 6 unit apartment building with (2) 2 bedroom and (4) one bedroom units. It was serviced by two 50 gallon gas water heaters. In my 3-4 bedroom houses, they all have 40 or 50 gallon water heaters which covers a family of 4-5. As others suggested, you may want to consider tankless on demand or even hybrid. Have a plumbing professional put together proposals.

One hot water heater for 32 Units... enough?

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