generally you put one main in and tie everything into it - this applies to hung sewer (like a house with a basement/crawl) or a buried one under a slab. there'll only be one pipe going to your septic tank from the house.

obivously this is just a basic example. but you get the idea.

All reloading info shared is based on my experiences in my guns. Follow safe reloading practice and work up loads from published minimum data.
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