Waterstops--Cast-in vs Synkoflex

We spec both Synko flex and PVC types. For the most part, a critical joint gets PVC. Sometimes you want to have a portion of a basin down and no water rushing under common walls. This is a good location for Synko Flex. Also, this stuff doesn't work all that great in vertical applications like wall bulkheads of slabs or walls. The sun hits it and it begins to grow and fall off. We've had this happen by many different contractors. Synko flex works better at the base of walls.

The problem with PVC in cantilever structures is getting the steel around it. It's not difficult, but does take some special detailing.

Also keep in mind how you transition between joints in the slab to the wall. These "connections" can be a location of leaks. Especially if you transition from PVC to Synko Flex.

Good luck.

I'd ask how much of a credit they're offering to make the substitution. If it's negligible or nothing make them use PVC.