I have the most frustrating plumbing issue in my basement which is on a sump pump for the sewage (one toilet, one tub, and laundry).
The area where the pump is has backed up again and again Each time, the plumber suggests putting in a new pump (saying the old one must be faulty). I've had three new pumps put in and the problem still occurs. I called an electrician - wiring has been okayed - no issue.
When we think we've fixed it by lifting the pump and getting things going again, it runs for a few days, then backs up.. Seems to be the load of water going in can't be handled by pump, but it works fine for up to a week or two with the same amount of flushes, etc.
I am at wit's end and wondering if anyone out there can help me with advice.

That's not a sump pump, You have a ejector/grinder pump. Did you ever figure out just was clogging the system? Is the pump up on bricks of flat in the pit? Most of the ejector hookups have a toilet, lavatory and shower. You have a washer discharging into the pit. This means lint, Perhaps if you put a silk stocking over the washer hose it would cut down on the amount of debris going into the pt.

Now tell me how you've vented the system. There should be a vent on the lavatory and another on the washer trap. Both of these can tie back to the house vent system. There should be a vent coming out of the pit. The vent MUST be a dedicated vent and not tie into anything. It should terminate outside the house on the roof. Are your vents set up like that? If not then explain how they go. Back to you, Tom

For speedball1 - your answer was excellent and fast. I wanted to thank you. First, to help in letting me know what I have re: type of pump, and the considerations of venting. A development happened yesterday which you will find hard to believe. The check valve ended up being faulty. The off- and on- pattern was due to the general deterioration of the part, although it was hard to diagnose perhaps because of all the new parts and the 'newness' of the system. Goes to show you that new doesn't mean long-lasting. Again, I want to thank you for taking the time to answer and help out. You are a good guy Tom!

Thanks for the update. Did the check valve fail because it was clogged with lint build up? I still think you should tie a silk stocking on the hose to filter out the lint. Regards, Tom

That is an excellent idea and we are putting in an alarm system for the pump as well (it's on order) so when the plumber comes to install, I will ask him to do that. It's hard to get at the back of our stacker (next to impossible) so I know the plumber won't be crazy about trying to pull it out to do that, but I'll ask. It's not clear what happened to make the check valve fail, but it may have been lint (over the last few 2 years - but the laundry wasn't used that much).I can see how lint might get tangled up around it.
Thanks for your advice and time. Where do good guys like you come from?

Where do good guys like you come from? We come from all parts of the country. I can't speak for the rest of the experts but for me it's a way of giving back some of the knowledge I've picked over the years instead of simply letting it die with me.
I'll be 85 soon and I want to feel like I still have something left to contribute. I never wanted to turn into some old retired fart in Flordia setting in front of the TV waiting to die. Not my style! But that's just my story. Every one of our experts has his own story to tell.
Have a happy new year, Tom