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.

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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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