Keeping Energy From Running Down The Drain

Nearly 60% of heat wasted by drain water can be recovered with this simple system.

Have you ever thought about where all the warm water goes after you take a shower or wash the dishes? It simply runs down the drain and takes a lot of heat (and money) with it.

This is where Drain Water Heat Recovery (DWHR) comes in. It’s a smart, simple way to capture some of that heat and put it back to work in your home.

Let’s look at how it works, why it matters, and how it can help you save energy while reducing your utility bills.

What Is Drain Water Heat Recovery?

When you use hot water, it eventually flows down your drainpipes. Wastewater contains a substantial amount of useful heat energy. The drain water heat recovery system prevents the mixing of wastewater with the incoming cold water; instead, it transfers only the heat from the drain water to the fresh cold water.

A drain water heat recovery system is a device installed in your plumbing. As the warm wastewater flows out, it passes through a heat exchanger, basically, a special coil or pipe that transfers heat to the incoming cold water.

Think of it as recycling heat before it disappears into the sewer.

Here’s a simple way to picture it:

• Warm water goes down the drain
• The heat recovery unit absorbs the heat
• That heat warms up the cold, fresh water coming into your water heater
• The water heater uses less energy to reach the desired temperature

Why Should You Care?

Because it saves energy and money. Here are just a few of the benefits most homeowners see when they install a DWHR system:

• Lower Energy Bills: Since your water heater doesn’t have to work as hard, you use less electricity or gas
• Fast Payback: Many systems pay for themselves in just a few years through lower utility bills
• Reduced Carbon Footprint: Using less energy is good for the environment. You’ll cut CO₂ emissions every time you shower
• Long Lifespan: These systems have no moving parts and often last 20 years or more with minimal maintenance

Where Is It Installed?

Most drain water heat recovery units are installed where your main drainpipe carries warm wastewater, usually below the shower or near your water heater. They work best in homes where showers and hot water use are frequent because that’s when the heat recovery makes the most significant difference. When building a new home, it’s a good idea to stack bathrooms vertically above the DWHR unit to help it work more efficiently.

Is It Worth It?

If you’re building a new home or renovating your plumbing, installing a DWHR system is usually a smart investment. Even in existing homes, many homeowners find the savings and environmental benefits worth the cost. Typical systems are simple, passive, and require no additional energy to operate. Over time, the savings can really add up.

A Real-Life Example: A Net-Zero Home in Action

The Next-Gen home installed a Power-Pipe R3-60 Drain Water Heat Recovery Unit. The sensor data from this system shows just how effective it can be:

Efficiency: According to the sensors installed in the home, the system recovers about 59% of the heat energy from drain water, meaning nearly 60% of that wasted heat is put back to use.

Annual savings: The energy simulation shows that without a drain water heat recovery unit, annual energy use was higher. With the unit installed, annual energy consumption dropped significantly, resulting in annual savings of about $85. Over the years, these savings really added up.

Cost: The Power-Pipe R3-60 Drain Water Heat Recovery Unit costs about $640 CAD to purchase and install at the Next-Gen home. 

Payback period: With the annual savings of about $85, the payback period is roughly 7.5 years. After that, the system continues to save you money year after year.

Bottom Line

If you care about energy efficiency, sustainability, and lowering your bills, a drain water heat recovery system is a smart addition. You’ll waste less heat, spend less on energy, and feel good knowing you’re making the most of the resources you already use.