Turn on the shower, then wait. And wait. In a big house, or one where the water heater is at the far end, the cold water sitting in the pipes has to run down the drain before hot water shows up. A hot water recirculating pump is built to fix that.
How it works
Without recirculation, the water in the hot line cools off between uses. ENERGY STAR describes a demand recirculating system this way: when it's activated, the pump sends that cooled water back toward the water heater and pulls hot water up to the fixture, so it's ready when you turn on the tap.
The main types
With a dedicated return line. Noritz describes this setup as a cold line, a hot line, and a third line that carries water back to the heater. Many homes don't have that third line.
Without a return line. There are options for homes that don't:
- A built-in or integrated pump, which Noritz says is ideal when a home lacks a return line.
- A crossover kit, sold with the water heater, that stands in for a return line.
- A thermal bypass valve at the fixture farthest from the heater. Rinnai uses this approach, so homes without a dedicated return line can still recirculate.
How it's controlled (this part matters)
- On demand: you press a button, or a motion sensor turns it on, and the pump runs until the water is hot. Noritz calls the on-demand type the most efficient.
- Timer: the pump runs only at set times, like weekday mornings.
- Always on: convenient, but ENERGY STAR warns that systems that run continuously can use more energy than they save, between the pumping and the heat lost from the pipes.
So the goal is a system that runs when you need it, not around the clock.
Is it worth it?
It tends to make the most sense when:
- Hot water takes a long time to reach some fixtures
- The water heater is far from the main bathroom or kitchen
- You're replacing a water heater or switching to tankless anyway, when adding it is simpler
Every gallon you don't run down the drain waiting counts here in the desert.
Talk it through
If you're tired of waiting for hot water, ask us about recirculation the next time we're out, or when we quote a water heater or tankless install. We'll look at how your plumbing runs and whether a return line, a built-in pump or a bypass valve fits your house. OX Plumbing answers 24/7, and our $99 service call covers the visit, the diagnosis and an upfront price.