Dual dump valve with Y / individual blade valve replacement?

Assembly is slip fit/GLUED to drain pipe so you would have to CUT pipe into, shorten the pipe so you could use a coupling on each side with short piece of pipe to GLUE new assembly in place

Replace the valves via bolts in flanges.

I would unbolt the pipe side of flanges on each dump valve and remove as a WHOLE (valves and drain outlet still bolted together)
Then remove other bolts/valves...install new valves onto drain outlet and install as a UNIT--then bolt it up to drain pipes on each side