Sent by SandraEditor: Here's what our friends at Green Home Guide have to say:
Answered by Alex Georgiou, Recurve Inc.
We deal with this problem all the time.
If you simply want to stop wasting water, the recirculating system is the best option for you.
On-demand vs. timer
Assuming you do go with a recirculating system, the next decision you have to make is about the kind of pump to put in. These systems can either be equipped with a:
- recirculating pump that works in true on-demand mode, or
- the recirculating system can run continuously on a timer.
Obviously, the on-demand pump is the most environmentally friendly option, as it only operates when it is needed. One product we install a lot here at Recurve is the Metlund Hot Water D’Mand system. The pump eliminates waste water by only allowing water out of the faucet when it is at the desired temperature.
- On average it takes 30-45 seconds for the hot water to be available at the sink.
- The pump may be operated by a switch placed next to the fixture, by a remote switch, or by a motion sensor.
- An added benefit of a circulation pump is that you get hot water readily available to all sinks on that plumbing line, unlike the under-sink option where you get hot water to only one sink.
If the 30-45 second wait is unacceptable, a continuous pump may be used to make hot water available immediately. These operate just like an on-demand pump, except they are running continuously instead of only when needed. If you opt for this system, make sure to put it on a timer so it is only running during peak usage hours.
Another option is the electric under sink on demand heater, which is preferable in cases where the homeowner needs instant hot water and cannot wait for the on-demand pump.
- The downside for these systems is that they are very inefficient and will cost you a lot on your electric bill due to their heavy electrical draw when activated -- most under sink models use at least 3,000 Watts when called.
- For this reason, we rarely install under-sink electric heaters.