apcom ut1 hot water recirculation pump for under sink - instant hot water recirculating system for tank type water heaters ao smith for technical support or installation questions, contact (833) 232-9706. the apcom hot water recirculation system model #ut1 is a great option for single pipe system homes without an existing hot water return line and up to 250 ft of household piping. this under sink recirculation system works with a standard hot water tank or indirect water heater and requires an electrical outlet under the sink. the system is fully automatic and controlled by built-in sensors and switches. the pump typically runs three to four times per hour for one to two minutes in order maintain instant hot water at the faucet. the most energy efficient circulator on the market reduces waste and operating costs so you can enjoy the comfort and convenience of hot water in your home without the wait.