Q&A for How to Install a Tankless Hot Water Heater

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Question

How do you determine what size of tankless water heater you need?

Rob Calame
Training Manager at Barnett Plumbing & Water Heaters
Rob Calame is a Training Manager at Barnett Plumbing & Water Heaters, based in Livermore, California, and the Lead Instructor of their Water Heater Training Program. Founded in 2005, Barnett Plumbing & Water Heaters specializes in servicing and installing all water heater types including tank, tankless, and heat pump water heaters throughout the Bay Area.

Rob Calame

Training Manager at Barnett Plumbing & Water Heaters

Expert Answer

Look at the gallons per minute, (GPM) of a tankless water heater to understand how much water it can provide. Then consider the number of bathrooms, the size of the house, and the length of the pipes. Finally, think about the amount of usage and the number of people living in the house. Add up the GPM of the amount of water you want ready at any time, and use that to purchase your water heater.

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Question

If I have hard water, do I need a water softener in order to use a tankless water heater?

Community Answer

If you have hard water, I would recommend a whole house water softener system regardless of the type of water heater you have. Hard water will cause a deposit build up inside the tank of your traditional tank water heater, which will cause problems. It will also cause deposit build up in the tankless system. Beyond that, it will cause additional wear on all of your fixtures.

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Question

Do I need to mount a gas tankless heater upright, or can it be laid on its back?

Community Answer

As with any gas appliance, heat rises so the unit needs to be mounted upright and leveled.

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Question

After I install this, will I have hot water immediately?

Community Answer

Once installed the unit will provide hot water in accordance with its rated "rise time." You will probably notice some lag between opening a hot water tap and the water from the tap being hot, similar to having a tank-style heater. The hot water still needs to get from the unit to the tap.

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Question

What do I do if I have a recirculating pump?

Community Answer

Tankless hot water heaters are "on demand," and cannot be used for recirculating systems.

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Question

What size wiring is recommended when installing a tankless hot water heater?

Community Answer

You will probably need 220 volt service (as with an electric dryer) with at least 60 amps.

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Question

If my tankless water heater is gas and I have a 1/2 inch gas line to the unit, will it work for a year and then have a problem?

Community Answer

It depends on what kind it is. If it is an under-$200 tank then yes, but if it is over that price then no, it will be over 2 and 1/2 years until you should start noticing any problems.

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Question

How can I insert batteries in the geyser?

Community Answer

If you were to put batteries inside the geyser, they would most likely burn out because it would be so warm. Plug it into a wall or somewhere instead.

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Question

Which side, hot or cold, should the expansion be installed?

Community Answer

Install it on the cold water side, between the cold water shutoff valve and the water pipe line coming in.

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Question

Can it be mounted or installed on the outside of a house?

Community Answer

It depends which type of tankless water heater you purchase. Do some research and planning before you install an outside unit. You will need a unit that's meant to be outside, as well as withstand the weather and temperatures. Keep in mind that outside units require more maintenance, especially in harsh climates and weather.

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Question

Where does the hot water pipe connect?

Community Answer

It is connected between the cold water pipe and the hot water pipe. Its heater functions as soon as water flow is detected and continues until the flow stops. Energy and money savings are made, as these tankless units are on only when used, opposed to older tank units that cycle all the time.

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