I still have mine from my previous coach. I have a built in flush now.
When we used the flush king it did as it should. The first few times you use it time yourself on how long you "back-wash". Keep in mind depending on the amount of water pressure at the campground will have an effect on how much water you receive in a certain amount of time. I use to flush three times. Once for 8 minutes, once for 5 minutes and once for three minutes. I naver had an issue with build up or faulty gauge readings.
(I still have mine but do not use it) PM me if interested.
Tiffin Allegro Bus, 425 Cummins powered Freightliner XCR, Camp Freightliner, Honda CRV, tow-N-4 Down, U.S. Gear Unified Tow brake, Blue-OX tow bar, TST Monitors, Seelevel II Monitors, Samsung Res Fridge, Progressive 50A-EMS, No Kids-No Pets, Full Time.