How often should you clean a safety tank in Kathmandu?

The short answer

For most Kathmandu homes, a safety (septic) tank should be desludged every 2 to 3 years. Households with more people, or a smaller tank, need it sooner.

What actually drives the interval:

• Tank size relative to the number of people using it
• Water use — more flushing and washing means faster fill
• What goes down the drain — grease and solids shorten the cycle
• Ground conditions — a slow soak pit backs the whole system up

A rough rule of thumb you can estimate at home:

// people using the tank, and tank volume in litres
const years = Math.round((tankLitres / (people * 90)) * 0.6);
console.log(`Desludge roughly every ${years} year(s)`);

Treat that as a starting point, not gospel — book an inspection if anything smells off, literally.