{"id":5693,"date":"2026-07-29T11:39:06","date_gmt":"2026-07-29T11:39:06","guid":{"rendered":"https:\/\/bigwesttemp.com\/inhouseplumbing\/?page_id=5693"},"modified":"2026-07-29T11:44:38","modified_gmt":"2026-07-29T11:44:38","slug":"when-assumptions-are-treated-as-conclusions","status":"publish","type":"page","link":"https:\/\/bigwesttemp.com\/inhouseplumbing\/case-studies\/when-assumptions-are-treated-as-conclusions\/","title":{"rendered":"When Assumptions Are Treated as Conclusions"},"content":{"rendered":"
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When Assumptions Are Treated as Conclusions<\/h1>\n<\/div>\n<\/div><\/div><\/div>
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This case study examines how a large vent replacement proposal was based on assumptions rather than confirmed failure, and why diagnosis in full residential under-slab and underground cast iron sewer systems must match the actual failure mode before invasive work is performed.<\/p>\n<\/div>\n<\/div><\/div><\/div><\/div><\/div><\/div>

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The Situation<\/h2>\n

A homeowner contacted a plumbing company after noticing interior damage near a wall, which raised concerns about a possible sewer issue. She did not report persistent sewer gas odors or widespread plumbing problems.<\/p>\n

During that initial evaluation by another plumbing company, she was told that multiple vent stacks needed to be replaced. She was also told that the piping used in the system was \u201cincorrect,\u201d implying that prior work may have been done improperly.<\/p>\n

This was especially confusing for the homeowner because, when she purchased the home roughly six years earlier, she had been told the sewer system was new. Hearing that the \u201cwrong pipe\u201d had been used suggested to her that the earlier replacement may have failed or been done incorrectly.<\/p>\n

The proposal she received for this work totaled $75,106.29. Beyond the cost, what troubled her most was that the scope focused heavily on vent replacement and invasive work \u2014 without a clear explanation of how it would resolve the specific issue she initially called about.<\/p>\n

Uncomfortable with the scope, reasoning, and cost being proposed, she reached out to us for a second opinion.<\/p>\n<\/div>\n<\/div><\/div>

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Understanding the Existing System<\/h2>\n

Homes of this age commonly contain mixed plumbing materials, particularly when prior work has been performed over time:<\/p>\n

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  • PVC or ABS piping in walls and vent systems, often original to the home<\/li>\n
  • Cast iron originally installed under the slab<\/li>\n
  • PVC installed later during under-slab or underground replacement<\/li>\n<\/ul>\n

    All of these materials were code-approved and commonly used during their respective time periods. The presence of ABS vent piping does not indicate improper installation, incorrect material choice, or failure.<\/p>\n

    In this case, the most likely configuration was:<\/p>\n