Instant hot water without a return line
How an $80 recirculation valve under the furthest bathroom sink finally got hot water to the far end of the house.
Traditionally, hot water takes a while to reach the furthest sink in your house. It has to travel further, and the water sitting in the line goes cold in the meantime. About two years ago we replaced our water heater tank with a tankless unit. Impressed as I was by its size and efficiency, I still had the same problem: the kitchen and the bathroom took ages to get warm.
After some careful research I stumbled onto recirculation valves and how they interact with the recirculation pump built into my water heater. Since my house doesn’t have a dedicated return line, a recirculation valve was the only way to get hot water to my furthest sink instantly.
How does it work?
The water heater’s built-in recirculation pump turns on and pushes hot water out through the hot water line. Instead of stopping at the furthest sink, that hot water enters the recirculation valve and gets pushed into the cold water supply, sending all the cooled-off water back to the water heater.
While it’s running, both lines carry warm water — so it takes a minute to pull genuinely cold water out of the cold supply. The valve has a built-in thermostat that closes off the hot side at a set temperature, which keeps hot water from flooding the cold line.
The install
- Turn off the water heater.
- Switch the internal 2-way valve from internal to external.
- Close the unit back up.
- Go to your furthest sink and install the recirculation valve.
- Purge any air out of the valve.
- Head back to the water heater and turn on the recirculation settings.
- I tested with Always On first, just to verify the valve was working.
- Then I switched to Intelligent recirculation, which learns your hot water usage at that faucet and sends hot water there on a schedule.
A note on sink choice: I picked the bathroom sink instead of the kitchen sink. The kitchen is one stop before the bathroom on the same line, so the kitchen line fills with warm water on the way through. Kind of a two-for-one hack, if you will.
The parts
- Water heater: Navien NPE-240A2
- Recirculation valve: NaviCirc 30022965A
- The thread that pointed me in the right direction: r/Plumbing
Below is the field card I worked off of — the whole job, phase by phase, with the details that are easy to forget once you’re on your back under a sink. It remembers what you’ve checked off, so you can close the tab and come back to it.
Field card · Recirculation setup
NaviCirc + NPE-240A2
- Pump: internal
- Mode: External recirc
- Schedule: Intelligent
- Valve kit: 30022965A
Progress 0 / 21
Read first
- Power off the unit before you remove the front cover.
- Don’t touch the two front-panel DIP switches — on the A2 they’re only gas type and temp-lock. Recirc is set in the menu, not there.
- Don’t run the pump until the loop is fully purged — trapped air can damage it.
At the unit
water heaterMount the NaviCirc
far bath sinkAir purge
protects the pumpProgram Intelligent
front panel[Menu] ─► Recirculation Setting ─► [OK] │ ├─ No Recirculation ├─ External Recirculation ◄ SELECT │ └─► Mode: │ ├─ Always On │ ├─ Intelligent ◄ SELECT │ └─ Weekly (1 / 3 / 7 Day) ├─ Internal Recirculation └─ HotButton (skip)
How Intelligent works: it watches your hot-water demand over a 7-day cycle, then recirculates the next week to match. Give it a full week to dial in — the first few days it’s still learning. Prefer to set it yourself? Choose Weekly and program 1 / 3 / 7-day windows instead.