Common Causes of Low Water Pressure in Lower Mainland Homes

Low water pressure is one of the most common complaints in older Lower Mainland homes, particularly in communities like New Westminster, Burnaby, and the Tri-Cities where a significant portion of the housing stock dates from the 1960s through 1990s. The cause varies widely and affects the appropriate solution.

Galvanized steel supply lines — common in pre-1980 BC homes — corrode from the inside over time, progressively narrowing the effective interior diameter. As the pipe corrodes, mineral deposits accumulate further. The result is steadily declining pressure that worsens over years. Replacement with copper or PEX is the permanent solution.

Most homes have a pressure reducing valve installed where the city water main enters the property. A PRV limits incoming pressure to a safe range (typically 45–80 psi). When a PRV fails, it can cause either dangerously high pressure or near-zero pressure throughout the home. A licensed plumber can test and replace this valve quickly.

After a repair or maintenance visit, a shutoff valve that wasn't fully re-opened is a surprisingly common cause of low pressure in one zone or throughout the home. Check the main shutoff at the meter and any secondary shutoffs under sinks or behind appliances.

If pressure drops when more than one fixture runs at once, the issue may be undersized supply lines, an undersized water main, or a combination. This is common in older homes that were built before modern fixtures and the increased demand of multiple bathrooms.

An aging or failing water meter, or damage to the service line between the municipal main and the property, can also restrict flow. These issues are the responsibility of the municipality up to the property line, and the homeowner's responsibility from the property line into the home.

If you've checked obvious shutoff valves and the problem is widespread or worsening, it's worth having a plumber assess the system. Diagnosis involves pressure testing at multiple points, visual inspection of exposed pipe, and evaluating the age and material of your supply lines.