Tree roots and older water lines in Oakville
South of the QEW, many Oakville houses sit on lots with large trees and original services. A clay sewer lateral under a mature maple or oak is a common place for roots to enter. The house drains fine for months, then the basement floor drain or the lowest shower backs up after a stretch of wet weather. Camera inspection shows the roots and whether the pipe is still round or has already collapsed.
Older Oakville homes can also still have galvanized steel water lines inside the walls. Those pipes rust from the inside. You notice brown water when a tap is first opened, and weak pressure at the shower when someone runs the laundry. Replacing the worst branches, or the whole interior system, is more useful than swapping fixtures that were never the problem.
If the basement has backed up from the sewer, a backwater valve is worth checking against Halton's subsidy rules before any floor is opened. Damp basements near the lake are not always a plumbing leak. If the water is only on the floor after rain and the meter is not moving while every tap is off, the issue may be groundwater. If the meter is spinning, or the water is coming from a ceiling or a wall, that is a supply or drain leak and it should be shut off at the main.