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Recirculation with a tankless heater
Tankless heaters can still make you wait for hot water.
Updated · 3 min read
Straight answer
Tankless heaters need a minimum flow before they fire, so a far tap still runs cold for a while. Recirculation keeps warm water near the fixtures. Use a tankless unit with a built-in pump and recirculation mode, or an approved external pump and crossover valve.
What this covers
Why tankless can feel slower
A tankless heater fires only when flow passes its sensor. It then heats water that has to travel the same pipe as before.
Some users notice a cold slug: hot water, then a burst of cold as the unit restarts after a short pause.
Built-in recirculation
Some tankless models include a pump and a recirculation setting with schedules or on-demand triggers. Those often pair with a crossover valve under the farthest sink.
Hard water and recirculation
Recirculation sends water through the heat exchanger more often. In very hard water, like Monterey Park's 220 mg/L city well average from its water quality report, scale builds faster.
More frequent descaling, or a softener, keeps the exchanger clean.
Choosing a control
- On-demand: button or motion sensor runs the pump only before use
- Scheduled: runs during the morning and evening rush
- Continuous: keeps water hot all day but uses the most energy
FAQs
Can I add recirculation to any tankless heater?
Not every model supports it. Check the manual or ask the maker.
Will it raise my gas bill?
It can if run continuously. On-demand and scheduled controls limit the extra use.
Does a crossover valve work with tankless?
Many systems use one. The maker's instructions say whether yours does.
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