Why does my shower lose pressure when someone uses another tap?

Your shower loses pressure when other taps are used because your home's plumbing system has insufficient water pressure or flow capacity to supply multiple fixtures simultaneously. This is a common issue in Toronto homes, especially older properties built before modern plumbing standards.

The most likely culprit is undersized supply lines feeding your bathroom. Many Toronto homes built before the 1980s have 1/2-inch copper supply lines that simply can't deliver enough volume when multiple fixtures demand water. When someone turns on a kitchen tap or flushes a toilet, it diverts water flow away from your shower, causing the noticeable pressure drop.

Water pressure regulators can also be the issue. If your home's main pressure regulator is failing or set too low, you'll experience this problem throughout the house. Toronto's municipal water pressure typically runs 50-80 PSI, but older regulators may reduce this to inadequate levels. Additionally, partially closed shut-off valves at the water meter or main line can restrict flow to the entire house.

In Toronto's older neighborhoods like Cabbagetown or The Annex, galvanized steel pipes are often the culprit. These pipes corrode internally over decades, creating significant flow restrictions. Century homes frequently have this issue, where the pipes look fine externally but are severely restricted inside.

Specific Toronto considerations include the fact that many homes have been converted to multi-unit dwellings without upgrading the plumbing infrastructure. If you're in a basement apartment or converted unit, the original plumbing may not have been designed for multiple simultaneous users.

Professional assessment is recommended for this issue because it often requires pressure testing and flow analysis to determine the exact cause. A licensed plumber can measure your home's water pressure at multiple points and identify whether you need supply line upgrades, pressure regulator replacement, or valve adjustments.

Immediate solutions include installing a pressure-balancing shower valve (around $300-600 installed in Toronto) which maintains consistent temperature and helps with pressure fluctuations. For whole-house solutions, expect $2,000-8,000 for supply line upgrades depending on your home's size and accessibility.

Next steps: Have a licensed plumber test your water pressure and flow rates at the main line and throughout the house. They can determine if you need supply line upgrades, pressure regulator work, or valve replacements to solve this frustrating issue permanently.