Upon arrival turned water off to Rudd tankless heater, drained out system and installed new mixing valve delivered to customer from manufacture. Tightened all screw and out cover back on and tested tankless heater by starting in kitchen turning faucet on and running hot water for about 5 minutes, then turned faucet off. Next test was done at fixture with lower GPM in upstairs bathroom, ran hot water through lavatory faucet for about 5 minutes. Rudd Tankless heater is working properly.