The principal at Ulanan reads the rain gauge on the flagpole every morning. A year of her readings shows why the tank never ran dry.
Mrs. Dela Peña started reading the gauge in July 2025, mostly to see whether we were right. Here is what twelve months of her numbers say.
Wet months, and not so wet months
Eastern Samar has no real dry season. The wettest months are December and January, when Ulanan got more than 500 millimetres each. The driest were April and May, at about 120. Even then, it rained on more than half the days.
What the roof caught
Ulanan guttered 280 square metres of roof. At 80 percent efficiency, every millimetre of rain on that roof is about 224 litres in the tank. In January that meant well over 100,000 litres reached the gutters, far more than the tank holds. The overflow pipe ran into the garden for weeks.
In April it was closer to 27,000 litres for the month. The school uses about 900 litres on a school day, for drinking, handwashing and the canteen. That is roughly what one rainy afternoon brings in.
Why the tank is the size it is
We size each tank to last about two weeks of school days with no rain at all. For Ulanan that is two tanks of 7,500 litres. A bigger tank would sit half empty most of the year; a smaller one would run out in the longest dry spells.
What we learned
The numbers told us the gutters matter more than the tank. In the wet months, a blocked gutter loses thousands of litres a day. So the maintenance days now start with the gutters, and the teachers have a long-handled scoop to clear them between visits.
The storms
Two typhoons passed close to Salcedo in the twelve months. Each brought more than 150 millimetres in a day, and both times the gutters overflowed at the corners. The tank itself was full within hours. What the storms showed us was where the gutters needed wider outlets, and we fitted them on the next maintenance day.
How the school uses the water
About half of the daily 900 litres goes to handwashing, mostly before lunch. A third goes to drinking, through the two filter taps. The rest is the canteen and cleaning. The teachers have asked us for a second drinking tap at the far end of the block, and it is on the list for 2027.
Keep reading the gauge
Mrs. Dela Peña has kept reading it. If you would like the monthly figures for your own class, ask us and we will send the spreadsheet.
