Pool Evaporation Chart

Size 1/2" per week
evaporation
1" per week
evaporation
1 1/2" per week
evaporation
2" per week
evaporation
15' x 30' 141 gallons/week
606 gallons/month
281 gallons/week
1212 gallons/month
422 gallons/week
1818 gallons/month
562 gallons/week
2424 gallons/month
16' x 32' 160 gallons/week
688 gallons/month
320 gallons/week
1376 gallons/month
480 gallons/week
2064 gallons/month
640 gallons/week
2752 gallons/month
18' x 36' 202 gallons/week
868 gallons/month
405 gallons/week
1737 gallons/month
607 gallons/week
2605 gallons/month
810 gallons/week
3474 gallons/month
20' x 40' 250 gallons/week
1075 gallons/month
500 gallons/week
2150 gallons/month
750 gallons/week
3225 gallons/month
1000 gallons/week
4300 gallons/month

To prevent hundreds of gallons of water from being wasted, MMWD recommends installing a pool cover. Water is lost during the day due to evaporation, and at night, because of evaporation lost through nighttime temperature drop.

To use the chart, measure your weekly water loss at the pool's tile line (a grease pencil works well to mark the level). Then look up the pool size and amount evaporated on the chart to determine the approximate evaporation loss. For example, 1" decrease per week from a 16' x 32' pool equals 320 gallons of water lost per week.

Please note that this chart does not include "splash out." Including "splash out," the total annual water loss for a pool 20' x 40' may exceed 35,000 gallons.



Copyright 1998 Marin Municipal Water District. All rights reserved.