Yeah there is a big difference between “galvanized tanks” and “bladder style tanks” when it comes to check valves.
The air maker system of the galvanized tank needs an above ground check valve to work properly. The Schrader valve lets air in without causing a vacuum in other parts of the line. The pump starts against an air cushion in the pipe and pumps into a tank with another air cushion, so there is no water hammer.
A bladder style tank has no air maker system. So an extra check valve causes a vacuum below it and there is no air cushion to start the pump against. Transitioning from a vacuum to positive pressure the second a pump is started also causes tremendous water hammer in the system.
The old galvanized tank systems require two check valves.
Two or more check valves in a bladder style tank system will cause problems. It doesn’t usually cause problems right after installation, but it will soon, and at the most inopportune time.
The air maker system of the galvanized tank needs an above ground check valve to work properly. The Schrader valve lets air in without causing a vacuum in other parts of the line. The pump starts against an air cushion in the pipe and pumps into a tank with another air cushion, so there is no water hammer.
A bladder style tank has no air maker system. So an extra check valve causes a vacuum below it and there is no air cushion to start the pump against. Transitioning from a vacuum to positive pressure the second a pump is started also causes tremendous water hammer in the system.
The old galvanized tank systems require two check valves.
Two or more check valves in a bladder style tank system will cause problems. It doesn’t usually cause problems right after installation, but it will soon, and at the most inopportune time.