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Faster Hot Water

Dedicated Hot Water Return Lines - Are the Added Costs Justified?

Do dedicated return lines make sense in new construction?

I have been asked many times if it makes sense to add a temperature sensor to a dedicated hot water system in a new home to turn off the circulation pump when the back-end of a return line gets hot.

The reality is a dedicated return line no longer make sense - period.

Certainly we have to pay attention to costs when we are building a home. And we must consider water and energy conservation measures as well as long-term maintenance issues.

A hot water recirculation lines gets a negative rating (-) on 3 of the 4 criteria listed above. Here is a look at each facet to see why a dedicated line does not pass scrutiny.

Factors to consider

Cost (-):

Extra water pipes for the dedicated section of the water pipes increases construction costs.

Water Conservation (+):

They save water by having hot water immediately available when a faucet is turned on.

Energy Conservation (-):

They waste energy by keeping the pipes hot even when there is no demand for hot water.

Long Term Maintenance Issues (-):

Studies show that homes with dedicated hot water lines experience a much higher rate of pinhole leaks.

Why are circulation lines still being built?

It can be argued that circulation lines get hot water almost instantly which is a wonderful convenience in our fast paced lives.  However we only use hot water 2% to 3% of the time in our homes.  Having hot water running in a loop all of the time means that 97% to 98% of the time we are wasting energy to keep the loop hot just in case we need hot water.

Re-circulation systems that use a cold water line to return the cool water in the hot line to the water heater changed everything. Now we can have our cake and eat it too.

Installing a re-circulation pump at the water heater and bridging the hot and cold lines underneath the farthest sink meets allows the cool water in the hot line between the water heater and the farthest fixture to be pushed back to the water heater and meets all 4 criteria listed above.

Cold water line circulation systems

Cost (+):  

Cost range from $350 to $900

Water Conservation (+):

On-demand systems waste less than a cup of water

Energy conservation (+):

On-demand systems do not waste energy by keeping water lines hot - only run when there is a demand.

Long term maintenance issues:

Turning off circulation pumps when there is no demand for hot water virtually eliminates pinhole leaks.


There are multiple options available but the best systems are turned on by a hot water faucet, they are installed near the water heater (not under a sink) and they can be installed in about 2 hours.

So if you are building a new home you can save money now (lower construction costs) and reduce expenses when you move in (lower water, energy and maintenance costs).

If you decide to go forward with a return line a circulation pump controller that manages when the pump comes on will help keep your costs down.

Getting hot water quickly has never been easier than with an on-demand circulation system. If you have any questions please leave a comment below or contact me directly at the email address or phone number listed below.

Mark Franklin is a civil engineer, inventor and founder of Faster Hot Water. Mark has been involved in over $100 million in construction and is routinely hired by large hotel groups to solve hot water delivery problems.

Mark lives in San Diego with his 19 year old son and works with plumbers, builders and wholesalers around the US to promote smart building practices that promote water and energy conservation.

Contact information:

Mark Franklin 
(619) 665-2077

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