Catskill/Delaware Watershed

Protected Watershed · Northeast

Serves 9 cities in our database · ~3,287,692 residents

63
Avg Hardness (PPM)
22
Avg PFAS (ppt)
3.6
Avg Lead (ppb)
9
Cities Served
Soft
0Slightly
60Moderate
120Hard
180Very Hard
250Extreme
400+
63 PPM Moderately Hard
CONTAMINANT LEVELS Hardness 63 PPM TDS 107 PPM PFAS 22 ppt Lead 3.6 ppb Chlorine 1.1 mg/L Nitrate 1.4 mg/L

About Catskill/Delaware Watershed

New York City's water comes from a network of 19 reservoirs and three controlled lakes in the Catskill Mountains and Delaware River basin — the largest unfiltered surface water supply in the United States.

Geography & Hydrology

The watershed covers nearly 2,000 square miles in upstate New York, with reservoirs up to 125 miles from the city. The system delivers over 1 billion gallons per day by gravity alone — no pumping required. The Catskill Aqueduct, completed in 1917, is an engineering marvel.

How Catskill/Delaware Watershed Water Is Treated

Like Portland and San Francisco, NYC has a filtration avoidance determination from the EPA. Treatment consists of UV disinfection (the world's largest UV facility), chlorine, fluoride, and orthophosphate for corrosion control. The city invests heavily in watershed protection to maintain the exemption.

Across the 9 cities we track, water from Catskill/Delaware Watershed averages 63 PPM hardness (Moderately Hard), ranging from 27 to 120 PPM. This is relatively soft water - a water softener is generally not needed.

PFAS concern: Cities supplied by Catskill/Delaware Watershed average 22 ppt PFAS, exceeding the 2024 EPA limit of 4 ppt. An NSF P473 certified filter is recommended for drinking water.

Current Challenges

Development pressure in the watershed, aging infrastructure (century-old tunnels), climate change affecting precipitation patterns, and the costly Delaware Aqueduct repair project (one of the largest infrastructure projects in NYC history).

Cities Supplied by Catskill/Delaware Watershed

Water quality varies by city due to local treatment, distribution infrastructure, and source blending.

Philadelphia, PA

100 PPM · Moderately Hard 1,600,000 residents

Abington, PA

52 PPM · Slightly Hard 822,600 residents

Trenton, NJ

27 PPM · Slightly Hard 217,000 residents

Princeton, NJ

70 PPM · Moderately Hard 217,000 residents

Yonkers, NY

45 PPM · Slightly Hard 211,569 residents

Easton, PA

120 PPM · Hard 96,867 residents

Bensalem, PA

50 PPM · Slightly Hard 59,001 residents

New Brunswick, NJ

48 PPM · Slightly Hard 55,000 residents

Lawrence Township, NJ

55 PPM · Slightly Hard 8,655 residents

Recommended for Catskill/Delaware Watershed Water

Based on average water quality across 9 cities supplied by Catskill/Delaware Watershed.

PFAS Filter Clearly Filtered Pitcher ~$90 Test Your Tap Home Water Test Kit ~$30

Affiliate disclosure: we may earn a commission on purchases. Recommendations based on water quality data.

Frequently Asked Questions

Is Catskill/Delaware Watershed water safe to drink?
Water from Catskill/Delaware Watershed meets EPA safety standards in all served cities. However, average PFAS levels of 22 ppt exceed the 2024 EPA health guideline. A certified water filter is recommended for drinking water.
Why is Catskill/Delaware Watershed water soft?
Catskill/Delaware Watershed benefits from a protected watershed that produces naturally soft water with low dissolved mineral content.
How many people drink Catskill/Delaware Watershed water?
Catskill/Delaware Watershed supplies drinking water to 9 cities in our database, serving approximately 3,287,692 residents. The largest cities include Philadelphia, PA; Abington, PA; Trenton, NJ.
Do I need a water filter for Catskill/Delaware Watershed water?
Yes. With PFAS averaging 22 ppt, a reverse osmosis or activated carbon filter is recommended. Look for NSF P473 certification.