Plumbing – Will this slotted waste fit this basin

You can easily calculate how often regeneration will be necessary if you know how hard your water is. If you are using city water, they should be able to tell you otherwise there are kits you can use to test your water. And any softener salesman should test your water as part of sizing your system.

In my area, the hardness is measured in grains per gallon and the value is 10.

My water softener is rated at 30,000 grains so I need to regenerate after using 3,000 gallons of water. I use about 100 gallons per day so I regenerate every month.

This link gives you an idea of how much water is used during regeneration for several different brands of water softener: https://web.archive.org/web/20101007181800/http://www.watervalue.com/softener_regen_water_usage.html

Cut where marked, but adjust the location so you've got clearance to work later.

Seeing as you only need a couple of millimeters, you might be able to get away with buying only the coupling connector similar to this:

So a good straight cut where marked, insert the connect and solvent weld it back into place.

Take the cut piece in with you, and just make sure you've got a snug dry fit in the store. No need to actually figure out the exact diameter. Just buy the piece that fits.