where can i find some reef safe checkvalves

[intarsiabox]

If you're in the Edmonton area Marine Aquaria has the clear flapper valve with unions on each end for fairly cheap, they also have the ball check valves for more money but lasts longer. Just keep in mind when designing your system to never trust a check valve as they all can fail, leave enough room in your sump to capture all the water from the overflow from the display tank.