Code Question

Static Design

How do you figure out the hot water demand for lets say 3 bed, 2 full bath house?

And where in the code book says the water heater has to deliver enough hot water for the total demand of the house hold? I am not a plumber nor plan to be I just want it for argument purposes haha.

plumber1a

Hot water- 2- showers @ 2.5 GPM=5, 2- lavatories @ 2.5 GPM=5, 1- kitchen sink @2.5 GPM= 1.25, I split the demand in half as we usually mix out water 50% hot & cold. Now this is where we do a bit of assuming, assuming each shower is 20 minutes long 20x2.5= 50 GPH, hand washing is 5 minutes 5x2.5=12.5, dish washing 15 minutes 15x1.25=18.75 GPH. Total for all is 81.25 GPH demand. We now need to locate a water heater that will heat about 81.25 GPH to 120 degrees. My incoming minimal water temperature is 60 degrees, so I need to locate a heater that will heat 81.25 gallons of water 60 degrees within 60 minutes, I use my water heater specification sheet for this and located a 50 gallon, 40k BTU heater with 50 gallons of storage will work fine. Now if I have several occupants using the system, or have fixtures with higher demands I need to increase the heater size even more as we base the size on maximum peak usage demand. There are other way to also do this, hopefully this helps.

plumber1a

I forgot about the code section you asked. Chapter 5 of the California Plumbing Code for water heaters table 5-1 indicates the minimal size heaters, base upon your scenario 67 would be your minimal 1st hour rating.

neolitic

Doesn't that assume that your
average family of 3.5 is pretty
busy multi-tasking?

Not saying it wouldn't be "ideal"
but under normal use, it seems
there's a good deal of wasted
capacity and unnecessary energy
consumption.

Just a thought, not an argument.

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KillerToiletSpider

There is no code that says a house has to have hot water.

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neolitic

N/S???
21st century and all that....

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Static Design

Thanks for the replies, I wasn't sure if there was a code or not so I figured i'd ask the pros before making any assumptions.

KillerToiletSpider

You can get an occupancy permit for a dwelling without a water heater or hot water piping, provided there is a means to heat water in the dwelling.

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neolitic

So I wasn't out of compliance
for the week when the W/H
crapped out during "The Blizzard."


Been worried about that for 30 years.

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KillerToiletSpider

I am quite happy that I have been able to relieve you of thirty years of needless guilt.

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neolitic

It's good to have friends.

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bwalley

30 gallon water heater would be fine a 40 would be better though.

The most you would use at 1 time would be 2 showers and maybe a kitchen sink or a DW.