Many people are disappointed when they realize that tankless water heaters don’t provide instant hot water. Somehow there was a mix up in interpretation between instant and endless hot water.
All on-demand means when it comes to tankless heaters is that the water gets heated when you turn on the faucet. It doesn’t mean you don’t have to wait for hot water.
Depending on how far the fixture is from the tankless heater, you could be waiting a while for that hot water to arrive.
In this article, I will go over how to get faster hot water when you have a tankless water heater.
Why Do Tankless Water Heaters Take So Long to Heat Up?
Think about how tankless water heaters work and compare it to a tank system.
With a tankless heater, cold water enters the heat exchanger. If you live in a cold climate then this water can be really cold. It takes time for the element to come up to temperature. The water is passing through the element as it heats up so the first water to reach you is the cold water in the pipes and then the lukewarm water that passed through the element before it was up to temperature.
Once you get the water coming through at the desired temperature, it stays that way indefinitely. Endless hot water.
A tank system is always heating water. That’s one of the downsides. When you shut off the water, the tank is now heating up the new water that arrived in the tank whether you want it or not. The water in the pipes is still hot until it cools down due to sitting there.
Now, neither one provides instant hot water, but usually, a tank system gets hot water to you faster.
How to Get Faster Hot Water From a Tankless Heater
The answer is to have a recirculating pump. The way they work is to create a loop from the heater to your fixture. A thermostat detects when the water is cooling down and trips the heater to heat the water.
As soon as you turn on the faucet you have hot water. Basically, there is always hot water in the pipes circulating back to the heater as the water cools.
If you haven’t already bought your tankless water heater and want instant hot water, then make sure you buy one that already has the recirculating pump. Some don’t have the pump already but are set up with the capability to add one.
Tankless Water Heaters with Recirculating Pumps
Not every tankless has that capability, so if this is important to you then you have to make sure you get the right kind.
Here is a list of tankless water heaters that already have a recirculating pump built in:
What are the Options For a Recirculating Pump?
You have two options when it comes to setting up your recirculating pump.
Create a dedicated loop
You can have a plumber set up a series of pipes that create a loop from your heater to your fixtures and then back to the heater.
The downside to this is that it is expensive to set up. You’ll need to pay a plumber his usual labor cost plus the amount of pipe needed. How much pipe length you need depends on how far the furthest fixture is from the heater.
The recirculating pump is installed directly on the tankless heater itself so you’ll need a power source nearby.
Some houses already have this dedicated loop already installed so it pays to check it out as you may already be set up without needing one installed.
Under-sink comfort system
To avoid the expense of adding a loop of pipes to circulate the hot water, you can install a comfort system under the skin. In this case, there is a sort of toggle that connects the hot and cold water lines under your sink. As the water is heated, the water runs into the cold water pipe leading it back to the heater. When the pump is on, there will always be hot water right at the fixture as soon as you turn it on.
There is a downside, of course. Since you don’t have a dedicated loop, you may end up with lukewarm cold water or have to wait for the water to get cold at the fixture.
Which system makes the most sense for you depends highly on your budget.
You can install a comfort system yourself and many of them work with a tankless heater, thus saving money.
Creating a dedicated loop is expensive and not something you can do yourself. You’ll need a licensed plumber and will need to check to make sure the pump is compatible with your tankless water heater model.
Many of the recirculating pumps available have timers so they are not running all day. You can set them up to only heat the water in the pipes at the times when you are home and usually need hot water.
Recirculating Pumps You Can Use With a Tankless Water Heater
There are some recirculating pumps that explicitly state that they are not meant for use with a tankless water heater and others that say they are.
The reality is it depends more on the tankless water heater than it does the pump.
In the above section, I listed the on-demand water heaters that are already have built in recirculating pumps. Make sure you check that out if you haven’t already and then circle back here.
Here are a couple of tankless water heaters that are recirculating pump ready so you can use any pump with these:
- Exclusive Water Savings technology conserving up to 1, 100 gallons per year
- 199, 900 BTU (gas consumed per hour)
- Exclusive Hot Start Programming minimizes cold water burst by staying in...
- Recirculation pump ready kit ready
- For use indoor only
- Energy Factor of .82
- Built-in Rinnai Circ-LogicTM recirculation program cycles an external pump...
- Certified for Installation in Manufactured (Mobile) Homes
- Enhanced scale detection lessens possibility of serious, long-term damage...
FAQ About Tankless Heaters and Instant Hot Water
The answer depends on how far away the fixture is from the heater and a couple of other factors. If your fixture is on the opposite end of a large house or is a couple of floors up, expect it to take up to a minute.
A fixture right night to where the tankless is located may only need a few seconds to arrive. And point-of-use tankless heaters are almost instant since they are right under your skink.
The thickness and material of the pipes is also a factor. It all depends, unfortunately.
It only takes 15 seconds for the water entering the heat exchanger to come up to the set temperature. This depends on how high your temperature is set, and how cold the water is as it enters. Generally, not more than 15 seconds with cold water and high-temperature settings, however.
Also, if your tankless uses less than 140,000 BTUs then it may take a little bit longer to heat the water to the desired temperature.
Usually, people set their tankless to 120°F to 140°F. The best temperature is at 110°F, however, so you don’t have to mix cold water when showering or washing your hands. You’ll get higher Gallons Per Minute (GPM) by keeping the temperature lower. The downside is that your washing machine and dishwasher need the water to be hotter, hence, people keep the temperature high.
Wrapping It Up
I hope this cleared up the confusion about whether a tankless water heater provides instant hot water or not.
I do believe they are worth it even considering that you will need a recirculating pump to get faster hot water.
No situation is 100% ideal so you really need to understand your needs and wants before making a hard and fast decision.