1) Open link below so we are talking about same type of household systemhttp://waterheatertimer.org/Water-heater-recirculation-system.html
2) 15 minute interval is misleading.
Pins located on timer dial divide 24-hour day into 15 minute intervals.
You set timer pins and decide which 15 minute intervals you want ON-or-OFF. Do this by moving pins inward or outward with your thumb or ink pen. To check settings, manually rotate timer dial clockwise and listen for pump turning on-off..
Set timer pins for 4 consecutive 15 minute intervals, then timer runs for 1 hour.
After pins are set, then manually rotate dial to set current time.
Dial rotates as time passes, and pins click a lever that turns pump on-off.
3) 5-year Life span. Like all things plumbing, if you have hard water or sand-n-dirt in water lines, then pipes clog. And pumps clog.
Once motor begins to slow down, it overheats and burns out.
Water softener can keep sediment out of lines, but shortens life of water heater.http://waterheatertimer.org/Clean-sediment-out-of-water-heater.html
4) Real question: do you need a circulation pump? Do you need hot water at your faucet? Can you schedule hot water use, or does recirculation pump have to run several hours per day?
Recirculation pumps causes water heater to run more, the pump consumes 25+ watts depending on pump, and water savings claims of 15,000 gallons per year are fabrication.
Realistic water savings is 700-2000 gallons per year, assuming several folks in the home use water sporadically across a full day, and each time water is used people are waiting for hot water. It also assumes that you never want cold water at the tap and that refrigeration ice maker line prefers hot water to cold.
5) Add a comment for more free help.
Also take advantage of fixya phone service.
For a price, fixya expert speaks with you over phone while you work on pump/timer or any do-it-yourself project.
We are always less expensive than a service call.