Why sizing is the decision that matters most
Most water heater complaints we hear — lukewarm showers, the tank "not keeping up," a tankless unit that stutters when two fixtures run — trace back to sizing, not brand. A correctly sized unit from a mid-range manufacturer will outperform an undersized premium one every day of the week.
From the Good News Plumbing & Drain team — family-owned, CA licensed (#906746), serving the San Gabriel Valley since 2001.
Sizing a tank water heater
Tanks are sized by storage capacity and recovery rate. The practical shorthand for households:
- 1–2 people: 30–40 gallons
- 2–3 people: 40–50 gallons
- 3–5 people: 50–60 gallons
- 5+ people: 60–80 gallons, or consider tankless / dual tanks
Also weigh when your household uses hot water. Back-to-back morning showers stress a tank far more than the same usage spread across a day — that's where recovery rate (how fast the tank reheats) matters as much as capacity.
Sizing a tankless water heater
Tankless units are sized by flow rate (gallons per minute) at a given temperature rise. Add up the fixtures you realistically run at once — a shower (~2 gpm), a kitchen faucet (~1.5 gpm), a washing machine (~2 gpm) — and size to that simultaneous demand. In the San Gabriel Valley, incoming groundwater is relatively warm, which works in tankless units' favor: less temperature rise means more usable flow from the same unit.
The failure modes
- Undersized tankless + big household: the unit cycles or delivers lukewarm water when demand spikes.
- Ignoring the gas line: many tankless retrofits need a larger gas supply line; skipping this step starves the burner. This is the most common corner cut in cheap installs.
- Skipping maintenance in hard-water areas: our region's hard water scales heat exchangers. Annual descaling protects tankless efficiency; without it, capacity quietly shrinks.
Experience from the field
Our team installs and services both types across the valley — see the deeper comparison in tankless vs. traditional water heaters. When we quote a replacement, we measure simultaneous demand and check the gas line before recommending a size, and put the whole scope in writing.
Next step
Explore water heater installation and tankless water heaters, or if your current unit is misbehaving, start with water heater repair.
Get a sizing recommendation or call 877-447-4737 — 24-hour emergency service available.
