ZIP Code 94402
San Mateo County, California — San Mateo
What This Means
San Mateo County, California has moderately hard water, estimated at 65 mg/L (PPM). At this level, you may notice some mineral buildup on fixtures and inside appliances over time. A water softener is optional but can help extend appliance life. Most people don't notice significant issues at this hardness level.
What You Should Do
Hardness Details
| ZIP Code | 94402 |
| County | San Mateo |
| City | San Mateo |
| State | California (CA) |
| Hardness (PPM) | 65 mg/L — Moderately Hard |
| Hardness (GPG) | 3.8 grains/gallon |
| Classification | 61 - 120 mg/L |
Source: USGS Water Quality Portal, county-level median
Your Water Utility
| Utility Name | MOUNTAIN VIEW MOBILE HOME PARK |
| System ID | NM3550001 |
| Water Source | Ground water |
ⓘ Your utility may treat water before delivery, which can change hardness levels. Check your utility's annual Consumer Confidence Report (CCR) for exact hardness values.
USGS Monitoring Data
| Monitoring Stations | 67 |
| Range | 27 – 3530 mg/L |
| Most Recent Data | 2022 |
| Data Quality | Measured |
Source: USGS Water Quality Portal
Effects at 65 PPM Hardness
At 65 ppm, some minor effects are possible: slight soap scum on shower doors, occasional water spots on dishes and glassware. Sensitive skin may notice dryness after showers. Appliance efficiency is minimally affected, but you may see light mineral deposits on faucets over time.
Is San Mateo Water Safe to Drink?
Yes. Hard water at 65 ppm in San Mateo is safe to drink. The calcium and magnesium that make water hard are actually essential minerals your body needs daily. The World Health Organization confirms there are no health-based guidelines for water hardness.
At this level, taste is generally good. Most people will not notice a mineral flavor, and the water is perfectly suitable for drinking, cooking, and making coffee or tea.
Your Water vs National Average
San Mateo water at 65 ppm is 35% softer than the US average of approximately 100 ppm. This is close to the national average. While not urgently requiring treatment, monitoring for scale buildup is advisable.
Best Solution for 65 PPM Water
Consider a shower filter ($15–40) for skin and hair benefits. At 65 ppm, a KDF or vitamin C shower filter can reduce mineral contact during bathing. A whole-house salt-free conditioner ($300–800) is an optional but effective way to prevent minor scale buildup on fixtures and appliances without adding sodium to your water.
San Mateo County Water Hardness Map
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Frequently Asked Questions
What is the water hardness for ZIP code 94402?
ZIP code 94402 is in San Mateo County, California, with estimated water hardness of 65 mg/L (3.8 GPG), classified as moderately hard. The area is served by MOUNTAIN VIEW MOBILE HOME PARK.
Do I need a water softener in 94402?
With moderately hard water at 65 PPM, a water softener is optional. You may notice some minor scale buildup over time.
What county is ZIP code 94402 in?
ZIP code 94402 is in San Mateo County, California (CA).
Is San Mateo water hard or soft?
San Mateo water is classified as moderately hard with an estimated hardness of 65 ppm (3.8 GPG). This is moderately hard — some minor mineral effects may be noticeable.
Is hard water in 94402 safe to drink?
Yes, hard water in ZIP code 94402 at 65 ppm is safe to drink. The calcium and magnesium minerals are actually beneficial for your health. At this level, the water tastes normal and requires no filtration for drinking purposes.
Will 65 PPM water damage my appliances?
At 65 ppm (moderately hard), minor scale buildup is possible over many years but significant appliance damage is unlikely. Regular descaling maintenance is sufficient.
Do I need a water softener in San Mateo County?
San Mateo County has moderately hard water at 65 ppm. A softener is optional but can help if you notice dry skin or minor scale.
Is San Mateo water OK for aquariums and plants?
Generally yes. At 65 ppm, most freshwater fish and plants will do fine. Check species-specific requirements for sensitive fish.