The complaint
A two-story home near the top of a rise has a primary bathroom upstairs. In the morning the shower is acceptable. In the evening, especially when the kitchen sink or dishwasher is running, it drops to a weak stream. The owners have already replaced the shower head, with no change.
They suspect the city supply, because the problem seems tied to time of day. A friend suggests the regulator. Both turn out to be partly right.
The owners' week of readings
| When | Static psi | Working psi (tub + kitchen) |
|---|---|---|
| Weekday 6 a.m. | 64 | 48 |
| Weekday 7 p.m. | 56 | 30 |
| Weekend noon | 60 | 42 |
| Weekday 8 p.m. | 55 | 28 |
What the readings told the plumber
- Static swings modestly.Evening static is lower than morning, consistent with normal supply variation for a home high in its zone.
- Working drop is large.The drop from static to working is much bigger than expected, pointing to a restriction inside the house.
- Find the restriction.The main valve is fully open and the regulator strainer is clean, but the line feeding the upstairs is old galvanized pipe, narrowed inside.
- Combine the causes.Modest evening supply dips plus a choked riser explain why upstairs suffers most at night.
Two possible fixes
Raise the regulator
- Quick change
- Raises pressure on every downstairs fixture too
- Does little for flow through a narrowed pipe
- Treats a symptom
Replace the riser
- Restores flow to the second floor
- Requires opening a wall or ceiling
- Permit question for the City of Fullerton
- Treats the cause
Outcome in this example
The owners choose to replace the riser and leave the regulator setting alone. Afterward, the evening working reading upstairs holds much closer to static. The shower still varies a little with time of day, which is normal, but it no longer collapses when the kitchen runs.
Questions this example raises for your home
- How big is your drop from static to working pressure?
- Does the problem follow time of day, other fixtures, or both?
- What is the pipe material feeding your upstairs?
- Has anyone already changed the regulator setting to compensate?
Common questions
Are these readings typical?
They are invented for illustration. Your readings will differ; the pattern between static and working is what matters.
Would a booster pump have helped?
Not much, because the main issue was restriction, not supply.
Is this a real job?
No. It is a made-up example.
General information for Coyote Hills, not a quote or professional advice. In an emergency, call 911.