Your check valve is like 90% of the noise. The chunks and bangs anyway.
Silent check valve will change your life. Also only get the spring style. Like this. All others are junk
So find the correct size of valve for what size of PVC you have, e.g 1 1/2 " vs. 2".
Supplies needed:. Valves, PVC cement & cement primer. Potentially hack saw, PVC pipe, PVC coupler
The distance between the PVC pipes isn't predictable, your old valve will not be the same height as your new one. My PVC on my sump x2 was luckily the same, but my ejector pit was not. I had to go buy 2" pvc and a staight coupler and cut the pipe to size.
I installed this check valve on two of my sump pumps and it worked wonders. It's called the quiet check valve and it truly lives up to its name. Plus it's clear so you can see if it's actually working. Highly recommend.
CHECK VALVE QUIET CLR1.5 by BRADY MfrPartNo 0823-15C https://www.amazon.com/dp/B00JFF205Y/ref=cm_sw_r_sms_c_api_STyZyb947Y42Z
Cut the line, pull the pump, unscrew the connector, get an adapter and piece of pipe (probably 1 1/2) screw and glue as needed, use a Fernco to re-attach the pump.
Seriously it should take less than an hour.
Use one of these valves and no thump.
https://smile.amazon.com/gp/product/B00JFF205Y/ref=oh_aui_search_detailpage?ie=UTF8&psc=1
Do it when dry and not needed. Plan ahead , get your parts, take your time and feel the accomplishment.
Buy a silent check valve. https://www.amazon.com/Campbell-CHECK-CLR1-5-MfrPartNo-0823-15C/dp/B00JFF205Y
Campbell Check Valve Quiet CLR1.5 by Brady MfrPartNo 0823-15C, White https://www.amazon.com/dp/B00JFF205Y/ref=cm_sw_r_cp_api_glt_fabc_AWNME9S8XTH4GNR3XRYC?_encoding=UTF8&psc=1
I wanted to get one of these, I heard they help a lot. https://www.amazon.ca/dp/B00JFF205Y/ref=cm_sw_r_cp_apa_fabc_8rrYFbM6MDV6D
It shouldn't hurt. Below is the one I used and it's been great! No loud thunk when it closes which is nice. They have a couple different sizes depending on your pipes.
https://www.amazon.com/Campbell-CHECK-CLR1-5-MfrPartNo-0823-15C/dp/B00JFF205Y
Well first make sure it's not just a loose connection on top there.
If you do replace it, might I recommend a great replacement.