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Plumber Red Seal · Question

A homeowner complains about low water pressure in their upstairs bathroom, particularly when the downstairs toilet is flushed. The water main pressure entering the house is adequate. What is the most likely cause of this issue?

When multiple fixtures operate simultaneously and cause a significant pressure drop, it often indicates that the pipe diameter serving those fixtures is insuffi

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Question: A homeowner complains about low water pressure in their upstairs bathroom, particularly when the downstairs toilet is flushed. The water main pressure entering the house is adequate. What is the most likely cause of this issue?

Answer options:

  • A faulty pressure reducing valve on the main supply line.
  • Oversized branch lines to the downstairs fixtures. ✅ Insufficient pipe diameter for the combined demand of multiple fixtures.
  • A build-up of scale in the hot water heater.

Correct answer: Insufficient pipe diameter for the combined demand of multiple fixtures.

Explanation: When multiple fixtures operate simultaneously and cause a significant pressure drop, it often indicates that the pipe diameter serving those fixtures is insufficient to handle the combined demand. This leads to excessive friction loss and reduced pressure at other points in the system.

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