Why Your Water Pressure Is Getting Worse — And Why It Won't Fix Itself
You've been living with gradually weakening water pressure for months. Maybe years. At first it was barely noticeable — the shower took a few extra seconds to rinse shampoo. Now the upstairs bathroom is nearly unusable, two fixtures can't run simultaneously, and filling a pot for pasta takes five minutes. Here's what's happening inside your walls: your pipes are slowly closing shut.
In homes built before 1970 — which describes most of Burlingame, San Mateo, Hillsborough, and Millbrae — the original galvanized steel water supply pipes corrode internally over decades. Rust and mineral deposits accumulate layer by layer, reducing a 3/4-inch pipe to an effective opening the width of a pencil. No amount of faucet aerator cleaning or showerhead replacement will fix this. The restriction is deep inside the pipe system.
"We just thought our house had weak pressure — lived with it for years. GB showed us a section of our galvanized pipe they cut out. The opening was the size of a dime. After repiping, the shower felt like a completely different house. Incredible difference."
— Burlingame homeowner, Broadway area ★★★★★
The 5 Most Common Causes of Low Water Pressure
Not all pressure problems are the same — and the fix depends entirely on the cause. Here's what we check first:
1. Corroded Galvanized Pipes
The #1 cause in Bay Area homes. Internal rust buildup narrows pipe diameter by 50-70% over 40-60 years. Pressure drops gradually and worsens at elevation changes (upper floors). Fix: Partial or whole-house repipe.
2. Failing Pressure Reducing Valve (PRV)
The bell-shaped valve on your main line reduces city pressure to safe levels. When it fails (every 7-12 years), pressure drops suddenly throughout the house. Fix: PRV replacement ($300-$600, same-day).
3. Mineral Buildup in Fixtures
Hard water deposits clog aerators, showerheads, and cartridges. If pressure is low at one fixture but fine elsewhere, this is likely the cause. Fix: Clean or replace affected components.
4. Partially Closed Shutoff Valve
The main water shutoff or individual fixture valves may not be fully open — especially after previous repair work. Fix: Identify and fully open the restricted valve.
5. Undersized Supply Line
Homes that have added bathrooms or fixtures without upgrading the main supply line may have outgrown their pipe capacity. Fix: Upsize the main from the meter.
How We Diagnose Your Pressure Problem
Static Pressure Reading
We measure pressure at the main line before it enters your home. This tells us immediately whether the issue is municipal supply, your PRV, or internal pipes. Normal is 45-65 PSI at the hose bib.
Dynamic Flow Testing
We open fixtures in sequence while monitoring pressure drop. Significant drop when multiple fixtures run simultaneously indicates pipe restriction — the water can't flow fast enough through narrowed pipes.
Isolation Testing
We test individual branches of your system to identify where the restriction exists — main line, hot supply, cold supply, or specific runs. This pinpoints the exact section causing the problem.
Solution & Options
Once diagnosed, we present your options with clear pricing — from simple PRV replacement to targeted section repipe to full system upgrade. You choose the scope that fits your budget and goals.
"Upstairs shower was barely usable — thought we'd need to repipe the whole house ($15K). GB tested the system and found our 12-year-old PRV had failed. $450 replacement and full pressure was restored instantly. Honest diagnosis saved us a fortune."
— San Mateo homeowner, Baywood neighborhood ★★★★★
Quick Fix or Full Solution — We Offer Both
Sometimes the fix is a $300 PRV swap. Sometimes it's a section of corroded pipe. And sometimes the entire system needs replacement. We diagnose honestly and present all options:
"Three-story home in Hillsborough. Third-floor master bath had terrible pressure. GB repiped just the supply risers to the upper floor — didn't need the whole house done. Targeted fix, dramatic results, reasonable cost. Smart approach."
— Hillsborough resident ★★★★★
Don't Live with Weak Pressure Another Day
Low water pressure isn't just an inconvenience — it's a signal that your plumbing system is deteriorating. Left unaddressed, corroded pipes eventually develop pinhole leaks that cause water damage. The pressure problem you tolerate today becomes the emergency you deal with tomorrow.
We serve Burlingame, San Mateo, Hillsborough, Millbrae, San Bruno, Daly City, San Francisco, and surrounding communities. Same-day diagnosis appointments typically available.
Strong Pressure Is One Call Away
Stop tolerating weak showers and slow faucets. GB Plumbing diagnoses the cause and restores full water pressure — often in a single visit. Call now.
(650) 235-6443