Waste Line Main Trap Buildup

[bluefleetwood]

Hi guys,
I have a curious problem since the house was built in 2000. For the first 4 years before I discovered the problem, I would get a waste backup in the basement from the washer machine drains and slow draining through the house. Plumber comes and snakes it out when ever this occurs usually every 5-6 months. Plumber couldn't explain it or didn't want to stop the gravy train I guess.
I popped the clean-out of the house side of the trap and noticed this build up. Once it was so small a golf ball wouldn't fit through. So since then I've been scraping it away every 3 months or so. The photos attached are a 3 month buildup. Only on the house side. The septic side is always clear, no build-up. I am guessing its soap buildup....? What can be done to prevent this? Drain cleaner, enzyme, non acidic, doesn't help.

 

[Reach4]

It looks like you have water standing in your pipe. That is not normal. How deep is the water?

 

[Sponsor]

 

[bluefleetwood]

It looks like you have water standing in your pipe. That is not normal. How deep is the water?

You can see it in there. Where else would it go? It's only in the trap.

 

[Reach4]

OK . You said trap. Prior posts have said that whole house traps are not normally recommended. I forget why. I guess there is not a need and they might clog up?