Frequently Asked Questions

Find the main shutoff first, usually near the water meter or where the supply enters a garage. Turn it clockwise until it stops. Label it now, because searching for it during a burst pipe wastes minutes you cannot spare.

Undersized or partially blocked supply piping is the usual culprit. Galvanized lines narrow with corrosion over decades, so two fixtures compete for flow the pipe can no longer deliver. A pressure test and a look at the regulator will separate the two causes.

That knock is water hammer, the shock of moving water stopping abruptly against a closed valve. Loose pipe straps make it louder. Adding arrestors near quick-closing valves like washing machine and dishwasher solenoids absorbs the shock and protects joints from repeated stress.

Repeated use is not. Caustic products generate heat and attack cast iron, older plastics, and the seals at joints, while rarely touching the real obstruction. Mechanical clearing or hydro jetting removes the blockage itself instead of leaving softened material to reform downstream.

Once a year suits most properties, and more often for buildings over 50 years old or with a history of backups. An inspection covers supply pressure, visible piping, shutoffs, the water heater, and drainage behavior, catching small faults before they flood something.

Leave immediately, take everyone with you, and avoid light switches, phones, and anything that sparks. Call the gas utility from outside so they can shut the service. Once the line is safe, a licensed plumber can trace the leak and repair the piping.

A running toilet flapper is the most common answer, followed by an underground supply leak or a dripping irrigation valve. Shut every fixture, then watch the meter's low-flow indicator. Any movement means water is escaping somewhere the eye cannot reach yet.

Dry traps are the usual reason, common in guest bathrooms and floor drains that go months without any use. Running water refills the seal. Persistent odor after that points to a cracked vent, a failed wax ring, or a broken drain line.

Many do, particularly houses built before the 1960s. Galvanized steel corrodes from the inside, which shows up as rusty first-draw water, falling pressure, and pinhole leaks. Malcolm Plumbing & Mechanical repipes these systems throughout San Francisco, CA in copper or approved plastic.

Let it cool and bin it rather than rinsing it away. Hot water carries grease past the trap, then it congeals on cooler pipe walls further down. Strainers catch food solids, and periodic professional cleaning removes what daily habits inevitably leave behind.

It steps incoming street pressure down to a safe level for fixtures, usually somewhere between 50 and 70 psi. When the internal diaphragm wears, pressure climbs or swings, which stresses supply lines, water heaters, and toilet fill valves until something gives.

Sediment collecting at the bottom of the tank displaces usable volume and insulates the burner from the water. A failing lower element or dip tube produces the same symptom. Flushing helps early; past a certain point the tank has simply aged out.

Any point where drinkable water can meet a non-potable source qualifies, such as a boiler loop, an irrigation line, or a fire sprinkler system. If pressure reverses, contamination travels backward into the supply, which is exactly what backflow assemblies exist to stop.

Pavement does not stop them. Roots follow moisture and vapor escaping from a hairline crack or a loose joint, then widen the opening as they thicken. Camera inspection shows how far intrusion has progressed and whether cutting or replacement is warranted.

Water heater replacement, sewer lateral work, gas line alterations, and most repiping all require permits, and sewer work beyond the trap needs a side sewer permit from Public Works. Pulling them protects resale, insurance claims, and your own inspection record later.

Phantom flushing means water is seeping past the flapper into the bowl until the fill valve wakes up to top off the tank. A worn flapper seat or mineral film on the seal is nearly always behind it.

Yes, because cabinet bases absorb water quietly and mold establishes long before staining shows. Most under-sink drips come from a compression nut, a tailpiece washer, or a corroded angle stop, all of which are quick repairs when caught early.

Gurgling means air is being pulled through a trap because the vent cannot supply it fast enough. A partially blocked branch line or an obstructed vent stack is usually responsible, and the noise often precedes a backup by weeks.

Angle stops, supply hoses, toilet flappers, tub and shower diverters, and the water heater's relief valve and straps. Vacancy is the one window when nothing is behind a schedule. Malcolm Plumbing & Mechanical handles these turnover checks throughout San Francisco, CA.