SJW Flushing Truck with Worker adding hose to hydrant

How Does a Truck Clean Water Pipes?

Have you ever wondered how water pipes are cleaned? Probably not. After all, most pipes are buried underground.

But if you’re curious, and you suddenly imagined a San Jose Water (SJW) employee using a large sponge (that’s not how it’s done), read on to learn how we’ve added a powerful truck to our workforce to help to clean water pipes and continue to deliver high-quality water.

Why Does SJW Clean Water Mains?

Even though the water flowing through the mains has already undergone treatment, water pipes need to be periodically cleaned to make sure sediment is removed.

Water mains build up sediment, just like the pipes in your home. But there’s no need to worry. Sediment buildup in mains and pipes is naturally occurring (it’s primarily made up of sand from wells and oxidized iron) and does not pose a threat to our health.

Flush Water Pipes to Clear Sediment

To remove sediment buildup, water utilities need to flush out pipes. SJW used to flush high-speed water through water mains (up to a couple of thousands of gallons per minute) to stir up sediment and send it out to clean water pipes.


In fact, traditional flushing methods, for SJW’s distribution system, used to require up to 6 million gallons of water a year.

NO-DES Truck: A New Method of Flushing Water Pipes

In contrast with traditional methods, the NO-DES system provides effective flushing and sediment removal with minimal waste and it’s portable on the back of a truck.

The acronym NO-DES is short for Neutral Output Discharge Elimination System; the term “neutral output” means that the water supply remains the same after undergoing treatment.

How NO-DES Works to Clean Water Pipes

Instead of losing hydrant water to the street, the NO-DES system connects hoses to two hydrants and pulls water through a truck’s filter tank to remove sediment. The pressurized system has the ability to increase the velocity of the water to recommended flushing speeds, so sediment is effectively removed.

Water is sent through the truck’s filter and returned back to the main, so minimal water is wasted. Additionally, the system includes sensors that detect when the water is free from sediment.

Even though SJW customers can use their water during treatment, they may temporarily experience discoloration or cloudiness, so NO-DES flushing happens during work hours when most people are away from home for school or work. However, the water remains completely safe to drink.