Officials are asking residents and businesses in La Cañada Flintridge, La Crescenta and Pasadena to conserve water during an upcoming eight-day pipeline shutdown starting on Thursday.

The Metropolitan Water District of Southern California is upgrading one of its oldest water lines, which delivers drinking water to 250,000 people in the region.

Officials are asking the affected communities to refrain from outdoor watering, washing cars, hosing sidewalks, filling pools and leaving tap water running. Local agencies will use groundwater and other water sources during the shutdown.

During the shutdown, the Foothill Municipal Water District — which provides water for Altadena, La Cañada Flintridge and La Crescenta — will only be importing a fraction of the water it usually does, or about 600,000 gallons, from the Metropolitan Water District of Southern California.

While Crescenta Valley officials don’t expect water supply problems during the shutdown, the district is not permitting outdoor irrigation. Pasadena has also banned outdoor watering and Pasadena Water & Power is asking residents to cut use by at least 30%.

Metropolitan officials suggest residents put a bucket in their shower to collect water before it warms up and use the collected water to care for sensitive plants.

The water shutdown will not affect Glendale Water & Power customers.

A similar shutdown took place in 2011 and customers responded well, said Nina Jazmadarian, general manager of the Foothill Municipal Water District.

“Conservation by residents and businesses in the affected areas will be essential in helping complete the repair work without additional water service impacts,” she said in a statement.

Residents can visit www.mwdh2o.com and www.bewaterwise.com for more information.

-- Brittany Levine and Tiffany Kelly

Follow Brittany Levine on Google+ and on Twitter: @brittanylevine