ALPINE INSPECTION SERVICES, LLC

What Is Backflow and Why Is It Dangerous?

Nilufar Massdjedi
May 8
2 min read

Backflow is a serious risk to your drinking water—yet many homeowners have never heard of it.

Whether you own a home in Lake Tahoe, Truckee, or Reno, understanding how backflow works (and how to prevent it) is key to keeping your water clean, safe, and compliant with local water regulations.

💧 What Is Backflow?

Backflow happens when water flows in the opposite direction than intended—allowing potentially contaminated water to enter your clean drinking water supply.

This can occur when there's a sudden change in water pressure, such as during:

Fire hydrant use
Water main breaks
Frozen or burst pipes
Heavy irrigation use

If your plumbing system isn’t protected with a properly functioning backflow prevention device, this reverse flow can pull contaminants—like fertilizers, chemicals, or even sewage—into your tap water.

⚠️ Why Is Backflow Dangerous?

Backflow isn’t just a plumbing issue. It’s a public health hazard.

Common risks include:

Fertilizers or pesticides entering the water from irrigation systems
Pool water containing chemicals being siphoned back into your home
Hose-end backflow (e.g., when a garden hose is submerged in a hot tub or bucket of soap)

These contaminants can cause serious illness if consumed—and are the reason every major water district in the Tahoe Basin and Reno-Carson region requires annual backflow testing.

🛠️ What Is a Backflow Prevention Device?

A backflow prevention device (or assembly) is a mechanical valve installed on your water line that ensures water flows in only one direction—out from the public water system to your home, not the other way around.

These devices are required for:

Homes with irrigation systems
Commercial buildings
Fire sprinkler systems
Vacation rentals with hot tubs or second water sources

✅ How Do I Know If I Need Backflow Testing?

If you're in a district like:

NTPUD (North Tahoe Public Utility District)
TCPUD (Tahoe City Public Utility District)
TDPUD (Truckee Donner Public Utility District)
IVGID (Incline Village General Improvement District)
TMWA (Truckee Meadows Water Authority)

…then you likely received a backflow test notice from your provider. These water districts require annual backflow testing to protect the public water supply and keep your property in compliance.