Irish Hills Mutual Water Co, CA
Lead detected, under the action levels
Latest 90th-percentile lead: 2.8 ppb (monitoring period 2023-2025). The federal action level is 15 ppb today and drops to 10 ppb in Nov 2027; EPA's health goal is 0. Lead was measured in sampled homes but the 90th percentile is under both action levels. EPA's health goal for lead is zero, so test your own tap if your home was built before 1986 or anyone in it is pregnant or a young child.
Irish Hills Mutual Water Co at a glance
Irish Hills Mutual Water Co serves about 135 people through 58 service connections, which makes it a very small system under EPA's size classes. It is privately owned and draws groundwater, in San Luis Obispo County, California. EPA system ID: CA4000203; phone on file: 408-594-5913. They can tell you what your service line is made of and whether they pay to replace it.
Every lead result on file
That is down 4.5 ppb from 7.3 ppb in the period ending 2022. The highest 90th-percentile result EPA holds for Irish Hills Mutual Water Co is 7.3 ppb across 6 monitoring periods, none of them over 15 ppb.
| Period ending | 90th-percentile lead |
|---|---|
| 2025 | 2.8 ppb |
| 2022 | 7.3 ppb |
| 2021 | 2.7 ppb |
| 2020 | 5.8 ppb |
| 2019 | 0 (not detected) |
| 2018 | 0 (not detected) |
How Irish Hills Mutual Water Co compares
Of the 2,884 California systems with a lead result, the median latest reading is 0 ppb; 30 are over 15 ppb right now and 215 have gone over at some point. Irish Hills Mutual Water Co's 2.8 ppb sits at the 84th percentile in California and the 80th nationally (higher means more lead).
Neighbouring systems
71 other systems share San Luis Obispo County; 12 of them have a higher latest lead result than Irish Hills Mutual Water Co. If you are unsure which one supplies your house, the name on your water bill decides it.
| System | People | Latest lead |
|---|---|---|
| San Luis Obispo Water Department | 49,534 | 0 (not detected) |
| Atascadero Mutual Water Co | 33,307 | 0 (not detected) |
| City Of Paso Robles Water Division | 31,176 | 0 (not detected) |
| City Of Arroyo Grande Utilities Division | 17,963 | 0 (not detected) |
| California Mens Colony | 15,000 | 0 (not detected) |
| Nipomo Comm Services Dist | 13,771 | 0 (not detected) |
| City Of Grover Beach Public Works Dept | 12,701 | 0 (not detected) |
| Morro Bay Pw Dept - Water Division | 10,757 | 0 (not detected) |
| Templeton Csd | 8,041 | 0 (not detected) |
| Pismo Beach Water Department | 7,944 | 0 (not detected) |
Your move
Test your own tap with a certified lab first-draw sample; San Luis Obispo, CA may offer free or low-cost kits through the utility. If your own line is lead, replacing the private side runs about $1,200-$12,300 (EPA average about $4,700). Ask Irish Hills Mutual Water Co whether it covers that cost before hiring anyone - many utilities now do.
These figures describe homes the utility sampled, not your tap. Only your service line record or a test of your own water answers the question for your house. What a 90th-percentile result does and does not tell you: how to read a lead result. Systems that went over once often dip back under; here is what that means.