Water heater sizing

That size water heater may have been sized “correctly” when the house was built. Water heater size is not dictated by code it is a customer preference. There are no codes in a national code book that states a certain amount of occupants must have a certain size water heater. Definitely not a defect just maybe a note in the report. I had a daughter that could burn through a 50 gallon water heater in one shower. Some families may have three children that shower before the water heater is depleted. A high recovery water heater is an option as it adds 15 to 30,000 BTU to the burner. A tankless water heater is an excellent option depending upon location however water quality should be excellent if using a tankless water heater. For every 20 customers who request a tankless water heater for my business I would recommend it to possibly five of them. The water needs to be soft unless they enjoy flushing the water heater with a pump and chemicals once a month per manufacturers instructions.

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Possibly not. For instance a 40 gallon standard water heater will have 30 gallons of usable water and will replenish those 30 gallons in possibly 45 minutes to an hour. The high recovery 40 gallon water heater will have 30 gallons of usable water but will replenish those 30 gallons in possibly 30 minutes. High recovery vessel type water heaters are a very different animal from tankless water heater’s. Just look at the BTU rating on a tankless compared to a storage water heater.

This is a 5 year old thread.

Boy, this is an old thread…

The “size” of the water heater is not addressed by building codes, but the minimum recovery rate is. The code is not based on occupancy, rather, it is based on the quantity of bedrooms and bathrooms in the residence.

It is most certainly NOT a preference and an improperly rated heater is most certainly a reportable defect.

I’m curious as I am looking at my uniform mechanical code book can you refer me to the section that states a water heater must have a certain recovery rate and what that rate may be? I will give you a hint, it may say something like an adequate amount of hot water shall be supplied.

Also please refer me to the section that says X amount of bedrooms, bathrooms must have X size water heater? Thank you very much.

No need for your “hint”

Check your Plumbing Code:

501.1 Applicability. The regulations of this chapter shall govern the construction, location, and installation of fuel-burning and other water heaters heating potable water, with chimneys, vents, and their connectors. The minimum capacity for storage water heaters shall be in accordance with the first hour rating listed in Table 501.1.

From the 2018 Uniform Mechanical Code Book section 501.1. I’m not sure what code book you are using. I believe your quote came from the ICC not an American Code book. Every jurisdiction has codes adopted from the UMC and put their own spin on it. I still don’t see a specific code for water heater size based on bathroom or bedroom quantity. It’s not like sizing a septic and there is no hard number unfortunately. Thanks for your expertise.

Plumbing code, not mechanical…

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California code bro. Remember what I said about local jurisdiction. I’ve been a Chicago plumber and the codes are different in every city and county in Illinois. I have held a license in two states and currently have a plumbing contractors license. California has a separate plumbing code as well. The Uniform Mechanical cold is the baseline for local jurisdiction codes. Local jurisdiction can increase a code but can’t decrease the code. Best to stick to quoting codes for your local jurisdiction if you dare. I would not recommend it as a home inspector. You might run into a guy that know a thing or two.

I did a search on the link you sent for my current state and guess what…zero reference to sizing a water heater. Be careful when you enter a contractors swim lane and start throwing codes around. Just friendly advise. Codes are often amended and updated. I can’t emphasize enough how we home inspectors must never quote codes. I will rarely call out a code violation unless it endangers the safety of the occupant and even then I recommend a licensed contractor evaluate the violation as I cannot fix it according to my code of ethics. Putting this one to bed.

PS plumbing falls under mechanical when you mention water heaters. The two code books are very similar and are used together as the reference each other in codes. Plumbing is DWV and water distribution.

Nice resource Jeff, thanks for sharing!

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Look “bro.” I won’t try to tell you what Chicago codes require, but I would venture a guess that recovery rate and/or tank capacity is addressed when sizing water heaters for residential construction in almost every jurisdiction. Otherwise, what’s to stop a builder from placing a 30 gallon water heater in a 5,000 sq ft, 6 bedroom 6-/12 bath home. It certainly isn’t “personal preference,” but I’ll let you do your own research on that.

As for the “stay in your swim lane” comment, I’m perfectly fine using the whole pool. Licensed contractors are the reason I have a job. And I will continue to quote code when necessary.

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