How many users can an on-demand hot water heater accommodate at the same time?

by Water Heaters on May 12, 2010

I am considering an on-demand hot water boiler/domestic water heater combo in Ontario Canada and am wondering how many of the following it would be able to support the following at the same time:
- shower/bath
- dishwasher
- clothes washer


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{ 5 comments… read them below or add one }

lpgnh3 May 12, 2010 at 7:42 pm

The on demand manufactures all make various sized units. Your best bet is to find the brand name you like, and then pick the model that will handle your needs.

Steven A May 12, 2010 at 7:42 pm

You have to determine the flow rate that you need (max) and buy the right size unit. Some will only supply one faucet at a time to supplying the whole house.

psioni May 12, 2010 at 7:42 pm

To establish this, you will need to estimate the rate of water flow you need from each source, i.e., washing dishes and taking a shower.

Assuming these activities may sometimes be done simultaneously, youll want to add those flowrates together and compare tankless water heaters that have an adequate water-heating capacity to accommodate the two activities.

Tracy S May 12, 2010 at 7:42 pm

I have a 40 gallon hot water heater in my house that serves 2 showers ,heavy duty washing machine,bath tub along with dishwasher with no problems.You have to think of how many devices will you be using at the same time.Next thing to decide is if you want a gas or electric water heater.

michael g May 12, 2010 at 7:42 pm

Who would run the dishwasher with the washer?

Not only putting unnecessary demand on the water heater but just the availability of water supplied to the residence. And shower too. Even with anti-scald valve bodies in your showers you will lose water pressure. Not thinking.

I have a 40 gallon gas water heater. I run 3 1/2 baths, washer, dishwasher and underground sprinkler system off my water supply but rarely two, never mind all of them. Maybe someone gets a drink while the washer is running or flushes a toilet but that’s iIf I converted to a wall mount instant heater I’d buy one rated to supply the equivalent of a 40 gal. heater. In this case, smaller is better.

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