Can wet volcanic ash clog drains?

MANILA, Philippines – It's true – wet volcanic ash can clog drains on roofs, as posts on social media say. (READ: What to do before, during, and after a volcano eruption)

According to GNS Science, the New Zealand government-owned earth and science research institute, it's best to sweep ash off a roof, because "the addition of water will turn the ash into mud which can set like concrete." (LOOK: Houses, trees in Calabarzon, Metro Manila covered in ash day after Taal Volcano eruption)

The United States Geological Survey (USGS) also advises against using large amounts of water to clean ash off roofs, as this may cause the ash to form a "glue-like 'cake' material," which will be difficult to remove and add more weight to the roof.

They also recommend not flushing ash into drains or downspouts, as this may cause them to clog. Instead, they recommend shoveling the ash to remove the bulk of it, then brooms to sweep the ash and place them in bags to reduce remobilization.

Residents in several areas, including Calabarzon and Metro Manila, woke up to ashfall on Monday, January 13, after Taal Volcano spewed ash and lava amid an impending eruption. (LOOK: Ashfall from Taal Volcano spreads to Calabarzon, Metro Manila)

State volcanologists raised Alert Level 4 on Sunday evening, January 12, warning that an eruption may occur within hours or days. – Rappler.com