How Much Hot Water Do I Need?

    How much hot water do taps, showers, appliances, and various other items use in our homes? When considering a tankless water heater this is interesting information to know and understand.

    There are a few points here we need to get out of the way.

    Pipe diameter – it doesn’t matter what type of water heater you have a ½ inch copper pipe can only provide around 11-19 liters per minute (3-5 GPM) of water. Once you reach the peak flow the only way to increase water quantity is by increasing your water supply pipes diameter.

    Pex pipe – If you are in a newer home you probably have pex running throughout your basement and walls providing all the water. Pex has a bit of a smaller diameter than copper pipe and thus it has a reduced flow. Most ½ inch pex pipe has a maximum flow rate of 7-11 litres per minute (2-3 GPM).

    Now, How Much Hot Water Do You Need?


    When comparing both a tankless and a conventional tank type water heater you need to know the differences. First off, a tankless heats water instantly and is more advanced in that they have a digital display on the front where you can set the exact temperature desired. This is beneficial in that you can keep your homes hot water temps relatively low and significantly reduce any chance of scalding. A tankless also provides and unlimited supply of hot water to fill your over sized tub or maybe back to back showers.

    Conventional Tank

    A conventional storage tank has a limited reserve of hot water and needs to be kept at a much higher temperature. The hotter temperature allows for a smaller amount of hot water to be mixed with cold water to make the desired water temperature. This works to prolong the hot water in your tank by only removing a minimal amount of hot water. Storage tank systems also need to be kept really hot to prevent the growth of legionnaires disease that can form within the tank.


    How Much Hot Water Do Typical Systems Consume?

    Typical Flow Rates

    LocationLiters Per MinuteGallons Per Minute
    Bathtub Faucet154
    Washing Machine11.43
    Shower9.5 – 11.42.5 – 3
    Kitchen Tap5.71.5
    Bathroom Tap5.71.5


    With the coldest incoming water you will likely experience in Ontario and a tankless you can expect roughly 19 litres per minute (5gpm) of hot water. This is a bit deceiving number that seems low but remember only a few appliances use the hottest hot water and the rest mix cold water in substantially reducing hot water demand. Your dishwasher, washing machine, and kitchen tap on occasion use as hot of water as you can provide. Your shower, taps, and bath really only ever call for water around 39 Celsius (102 F) as anything hotter would start to burn you. A tankless can thus actually power a fair bit more hot water applications than you would expect. Two showers and a dishwasher can easily be accomplished.

    This works for your conventional tank water heater as well as it only holds 40 or 50 gallons which isn’t much when you think about it. Since a lot of the hot water applications throughout the home don’t need super hot water it is diluted with cold to provide the desired temperature, this works to stretch out how much hot water your tank seems to hold.

    Final Thought

    Ultimately the choice is up to you, some people love their conventional water heater and thats completely fine. Some prefer the option of unlimited hot water, in which case a tankless would be the better choice. The good news is that we are here to service you; it’s your home, your choice.

    We install tankless water heaters as well a conventional water heaters. If you are located in Southern Ontario or the greater Toronto area we can get you a free quote.

    Give Us A Call (647) 925 1930 Or Click And Have Us Call You

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