Serving roughly 24,948 people in San Joaquin County, California.
Data current as of July 2026
🔍Straight from EPA
🧪Real Lab Results
📅Updated Quarterly
🏠Local Expertise
Results for CITY OF MOUNTAIN HOUSE
1 water provider directly on file, serving roughly 24,948 people in San Joaquin County, California.
Quick answer: CITY OF MOUNTAIN HOUSE has no violations on file. One reading is worth knowing about: Copper, Free was measured at 280UG/L, among the highest of the 571 providers on file in this area. It's the most notable figure in this system's record among its 571 local peers.
Lead Summary
Lead
Totalhaloaceticacids (HAA5)
TTHM
Chloroform
Bromodichloromethane
Dibromochloromethane
Bromoform
Dichloroaceticacid
Trichloroaceticacid
Dibromoaceticacid
Monochloroaceticacid
Copper, Free
Aggressive Index
Langelier Index (pH(s))
Magnesium
Hardness, Total (ASCACO3)
Calcium
Potassium
Sodium
Carbon, Total
Alkalinity, Total
Alkalinity, Bicarbonate
TDS
Sulfate
Chloride
Nitrate-Nitrite
Nitrate
Turbidity
pH, Field
Odor
Boron, Total
Vanadium, Total
Arsenic
Selenium
Zinc
Conductivity (at 25°C)
Color
Gross Alpha Particle Activity
Iron
Manganese
Utility CITY OF MOUNTAIN HOUSEPopulation served 24,948Owner Local government
No violations on file
Contaminants found
Metals
Naturally occurring or corrosion-related elements, e.g. lead, arsenic, copper
Lead Summary
Detected: 0 mg/L (ppm)
12/31/2025
Lead
Detected: 5 UG/L (ppb)
9/23/2025
A metal that can leach from old pipes, solder, and fixtures. Current medical guidance holds there is no truly safe level of lead exposure, especially for children and pregnant women.
Copper, Free
Detected: 280 UG/L (ppb)
9/30/2025
Vanadium, Total
Detected: 3 UG/L (ppb)
4/9/2025
Arsenic
Detected: 2 UG/L (ppb)
4/9/2025
Occurs naturally in some groundwater. Long-term exposure above the legal limit (10 ppb) has been linked to increased cancer risk and cardiovascular disease.
Selenium
Detected: 5 UG/L (ppb)
4/9/2025
Zinc
Detected: 10 UG/L (ppb)
4/9/2025
Iron
Detected: 150 UG/L (ppb)
4/9/2025
Mostly an aesthetic issue (metallic taste, staining) rather than a health concern at typical levels.
Manganese
Detected: 11.1 UG/L (ppb)
4/9/2025
Mainly a taste/staining concern at typical levels; long-term neurological research at high chronic exposure is ongoing.
Disinfection Byproducts
Formed when chlorine used to disinfect water reacts with organic matter
Totalhaloaceticacids (HAA5)
Detected: 10 UG/L (ppb)
9/3/2025
TTHM
Detected: 36 UG/L (ppb)
9/3/2025
A group of disinfection byproducts formed when chlorine reacts with organic matter. Long-term exposure above the legal limit has been linked to increased cancer risk in some studies.
Chloroform
Detected: 4 UG/L (ppb)
9/3/2025
One of the individual trihalomethane disinfection byproducts, formed when chlorine reacts with organic matter.
Bromodichloromethane
Detected: 10 UG/L (ppb)
9/3/2025
Dibromochloromethane
Detected: 15 UG/L (ppb)
9/3/2025
Bromoform
Detected: 7 UG/L (ppb)
9/3/2025
Inorganics
Common dissolved minerals and salts, e.g. nitrate, fluoride, chloride
Sulfate
Detected: 32.3 MG/L (ppm)
4/9/2025
Chloride
Detected: 44 MG/L (ppm)
4/9/2025
Nitrate-Nitrite
Detected: 0.4 MG/L (ppm)
4/9/2025
Nitrate
Detected: 0.4 MG/L (ppm)
4/9/2025
Commonly from agricultural fertilizer runoff or septic systems. Above the legal limit, it's an immediate concern especially for infants.
Boron, Total
Detected: 130 UG/L (ppb)
4/9/2025
Minerals
Everyday minerals that mainly affect taste and water hardness
Magnesium
Detected: 9 MG/L (ppm)
9/3/2025
Calcium
Detected: 13 MG/L (ppm)
9/3/2025
Potassium
Detected: 2 MG/L (ppm)
4/9/2025
Sodium
Detected: 34 MG/L (ppm)
4/9/2025
Properties
General water characteristics like pH, hardness, and cloudiness (turbidity)
Langelier Index (pH(s))
Detected: -0.3 LANG
4/9/2025
Hardness, Total (ASCACO3)
Detected: 69.5 MG/L (ppm)
9/3/2025
pH, Field
Detected: 8 PH
4/9/2025
Gross Alpha Particle Activity
Detected: 1.76 PCI/L
7/2/2025
Calculated Parameters
Values worked out mathematically from other test results, not measured directly
Alkalinity, Bicarbonate
Detected: 82 MG/L (ppm)
10/8/2025
Other
Additional substances tested that don't fit neatly into the categories above
Dichloroaceticacid
Detected: 3 UG/L (ppb)
9/3/2025
Trichloroaceticacid
Detected: 1 UG/L (ppb)
9/3/2025
Dibromoaceticacid
Detected: 6 UG/L (ppb)
9/3/2025
Monochloroaceticacid
Detected: 4 UG/L (ppb)
6/4/2025
Aggressive Index
Detected: 11.5 AGGR
4/9/2025
Carbon, Total
Detected: 1.3 MG/L (ppm)
10/8/2025
Alkalinity, Total
Detected: 67.1 MG/L (ppm)
10/8/2025
TDS
Detected: 210 MG/L (ppm)
9/3/2025
Turbidity
Detected: 0.1 NTU
4/9/2025
A measure of water cloudiness from suspended particles.
Odor
Detected: 16 TON
4/9/2025
Conductivity (at 25°C)
Detected: 355 UMHO/CM
4/9/2025
Color
Detected: 5 UNITS
4/9/2025
Filtration considerations: See the table below for how whole-house carbon, under-sink reverse osmosis, and under-sink carbon systems compare against what's actually on file here. These are general system types, not a specific product recommendation.