Is Mountain House, CA tap water safe?
Data: U.S. EPA · How we read the data · How we check it
Summary
No federal limits exceeded in EPA data for City of Mountain House.
City of Mountain House supplies Mountain House (26,400 people).
Water system
City of Mountain House
26,400 people · Surface water · EPA ID CA3910027
| PFAS | Highest average | Limit |
|---|---|---|
| PFOA Not detected | – | 4 ppt |
| PFOS Not detected | – | 4 ppt |
| PFHxS Not detected | – | 10 ppt |
| PFNA Not detected | – | 10 ppt |
| HFPO-DA (GenX) Not detected | – | 10 ppt |
ppt = parts per trillion. "Highest average" is the highest average at any of the system's entry points, the way EPA compares results with the limits.
Lead: 0 ppb at the 90th percentile (Dec 2025, and 9 in 10 homes sampled were at or below it) Below action level
Health-based violations since 2016: 0
Across California, 129 of 691 water systems EPA tested had PFAS above a 2024 federal limit, and 26 systems were above the lead action level in results from the last five years. California results.
Mountain House homes and lead pipes
Lead service lines and lead solder were allowed until 1986, so homes from before then are the ones to check. Renting? Ask your landlord what the service line is made of, because it's their pipe to replace. How to check your own line.
Housing: Census American Community Survey 2020–2024 5-year estimates for Mountain House CDP (tables B25034, B25003). Estimates for small places have a margin of error.
How nearby cities compare
| City | PFAS | Lead (90th pct.) |
|---|---|---|
| Tracy 6 mi City of Tracy | None above limits | 0 ppb |
| Lathrop 13 mi City of Lathrop | Above limit | 0 ppb |
| Livermore 13 mi City of Livermore | None above limits | 0 ppb |
| Brentwood 15 mi Brentwood Water System | None above limits | 0 ppb |
| Manteca 17 mi City of Manteca | Above limit | 0.4 ppb |
| Oakley 18 mi Diablo Water District | None above limits | 1.9 ppb |
Mountain House ZIP codes (1)
- 95391
Questions
Is Mountain House tap water safe to drink?
City of Mountain House has had no health-based violations since 2016. Utility data can't show lead from your own pipes: if your home was built before 1986, test your tap. Your utility's annual Consumer Confidence Report is the official summary.
Who supplies water in Mountain House, CA?
City of Mountain House, which serves 26,400 people.
Does Mountain House tap water have PFAS?
None detected above EPA's reporting limits. City of Mountain House had no PFAS detected in EPA's 2023–2025 testing. "Not detected" means below the reporting limit (about 2 to 20 ppt), not proven zero.
Do Mountain House homes have lead pipes?
Census estimates put 7% of Mountain House homes as built before 1980 (California: 56%). Lead service lines and lead solder were allowed until 1986, so older homes are more likely to have them. City of Mountain House's service line inventory says what your line is made of. The only way to know for your home is to check the line where it enters the house and test your tap.
Source: U.S. EPA drinking water records and PFAS testing (UCMR 5). How we read the data.