Gate Valve on 2" Ejector Basin discharge line

I know a gate valve is required on the 2" DWV line upstream from the check valve from the ejector pump basin. What's the purpose for the gate valve if it's always opened? Is it used to regulate/restrict the diameter to avoid possible air hammer/chatter during discharge?

I don't know about the type of valve, but I'd want a valve there in case I needed to repair, replace, or service the check valve, pump, or tank...you wouldn't want a hiccup letting the sewer back up on your head while you had things apart.

No it is to keep the sewage from draining back if you have to replace the check valve. It should be left in the wide open position at all other times...

Some systems can have quite a bit of head on them and without a valve it would be a bad day for a plumber and your basement!
Personally I would quote a really crazy $$$$ to do the work and sincerely hope that that you found someone cheaper to do it!

Ok...makes really great sense now. I'm doing the work myself and would not install the line without it....just never considerd the possible amount of "head" that could be in the line...or replacing the check valve.
Thanks!

Yea, I did a job on one where the line was on an uphill for about 400 feet... Imagine 400' of 2" dia. liquified poo coming at ya!

Fortunately there was a valve!