How to Install a Recirculation Pump
Updated February 20, 2026
Stop wasting water waiting for it to get hot -- install a recirculation pump using a dedicated return line or a comfort valve system (no new piping), with timer and sensor options.
Overview
Tired of running the faucet for a minute or two waiting for hot water? That wasted water adds up -- 10,000-15,000 gallons per year for a typical household. A recirculation pump keeps hot water moving through your pipes so it arrives almost instantly when you turn the tap. Two main options: a dedicated return line (separate pipe from the farthest fixture back to the heater, best for new construction) or a comfort valve system (no new piping -- a bypass valve under the farthest sink uses the cold line as the return). This guide covers both.
What You'll Need
Safety First
- The pump is an electrical device that mounts on the water heater. It needs a GFCI-protected outlet or hardwired connection. No extension cords.
- Comfort valve systems use the cold water pipe as the return line. That means cold water at distant fixtures may run lukewarm briefly while the pump is active. A timer that runs the pump only during peak hours minimizes this.
Step-by-Step Instructions
-
Choose the Right System for Your Home
Dedicated return line: a separate 1/2-inch pipe runs from the farthest fixture back to the water heater, creating a loop. The pump circulates hot water through this loop on a timer or continuously. Best for new construction where you can run pipe inside walls. True instant hot water with zero effect on cold water temperature. Comfort valve system: the pump goes at the water heater, a bypass valve goes under the farthest sink. The valve bridges hot and cold lines with a temperature-sensitive check valve. When hot water in the pipe cools below about 95-105 degrees, the valve opens and the pump pushes cooled water back to the heater through the cold line. When hot water reaches the valve, it closes. No new piping, installs in 1-2 hours.
Tip: For existing homes, the comfort valve system is the practical choice. Running a dedicated return line through finished walls is a major renovation. Comfort valve kits (Watts 500800, Grundfos Comfort System) include pump, bypass valve, and timer for $150-300. -
Install the Pump at the Water Heater
Turn off the water heater and cold water supply. The pump goes on the hot water outlet at the top of the heater. Disconnect the hot water pipe or flex connector from the outlet. Install the pump between the outlet and the pipe -- most pumps thread directly onto the heater nipple, and the pipe reconnects to the pump outlet. Teflon tape on all threaded connections. Make sure the flow arrow on the pump points away from the heater (toward the house). Check valve included? Install it as directed.
Tip: Most kits include isolation valves (shut-offs on both sides of the pump). Install them -- they let you remove the pump for maintenance or replacement without draining the system or killing the main water. -
Install the Bypass Valve at the Farthest Fixture (Comfort Valve Systems)
Find the fixture farthest from the water heater -- where hot water takes the longest to arrive. Under that sink, turn off both shut-off valves. Disconnect the supply lines. Install the bypass valve between the hot and cold valves using the supplied fittings and adapters. The valve bridges both lines with a temperature-sensitive check valve. Reconnect the supply lines and turn both valves back on. The bypass valve is passive -- no power needed, it operates automatically based on water temperature.
Tip: Multiple bathrooms far from the heater? Install bypass valves at more than one location for better coverage. Each additional valve ($30-50) extends recirculation to that branch of the plumbing. -
Set Up Timer or Sensor Controls
Running the pump 24/7 wastes energy heating water at 3 AM when nobody needs it. Most kits include a timer -- program it for peak usage times (6-8 AM and 5-9 PM, for example). Some systems use a temperature sensor or an on-demand button instead: the pump only runs when temp drops below threshold or when you press a button. On-demand is the most efficient but adds a 30-60 second delay.
Tip: Start with your obvious peak times and adjust after a week. Most households find two 2-hour windows (morning and evening) cover 90% of their hot water needs. Running the pump outside those windows is just wasting energy. -
Test the System
Turn on the water heater and cold supply. Plug in the pump (or flip the breaker). You should hear a quiet hum and feel slight vibration. Go to the farthest fixture and turn on the hot water -- should arrive within 5-15 seconds with a dedicated return line, 30-60 seconds with a comfort valve. Check all connections for leaks. Listen for unusual noises (grinding or clicking means a problem). Cold water at the farthest fixture may be slightly warm when the pump first kicks on but should normalize once the system cycles.
Tip: Hot water still slow at a specific fixture? It is probably on a different plumbing branch than the bypass valve. Add another bypass valve under that fixture. The pump pushes water through the path of least resistance, so distant branches may not get full coverage from one valve.
Pro Tips
- Insulate every hot water pipe in the recirculation loop. Without insulation, heat bleeds through the pipe walls and the pump runs more frequently. Insulated pipes retain heat and cut pump run time significantly.
- Operating cost with a timer: about $30-80 per year (electricity plus extra heating). But the water savings -- 10,000-15,000 gallons per year -- can save $50-100 in water and sewer costs. System often pays for itself or better.
- Tankless water heater? Check if it has built-in recirculation before buying a separate pump. Many modern units from Rinnai, Navien, and Noritz have a recirc port and internal pump -- you just need the return line or bypass valve.
- Comfort valve systems work best with simple plumbing layouts (one main trunk line). Manifold systems (multiple branches from a central point) need bypass valves at the end of each branch for full coverage.
- Pump clicking every few minutes? The bypass valve is cycling rapidly as water temperature fluctuates near the threshold. Normal but annoying. Running the pump in shorter timer bursts instead of continuously during peak hours reduces it.
When to Call a Pro
Comfort valve systems are straightforward DIY. Call a plumber if you want a dedicated return line through finished walls (major pipe routing), if your layout is complex and you need help with bypass valve placement, if the pump needs hardwiring (electrician territory), or if you have a tankless heater and want to use its built-in recirc feature.