How much water does a backyard rink need?
On level ground it is length times width times depth. One cubic foot holds about 7.48 US gallons, so every inch of water on a 20 by 40 ft rink is about 499 gallons. At 3 in (0.25 ft) that is 20 × 40 × 0.25 × 7.48 = 1,496 gallons. The tables below are worked out by the same code as the calculator, for a level yard.
Common sizes in feet
Every figure here is water at the stated depth over the whole floor. Other guides may use a different depth, which changes the total a lot: Pwice says a 20 by 40 ft rink at 3 in holds "approximately 1,800 gallons", while 3 in works out to 1,496 gallons here. 1,800 gallons is closer to 3.6 in of average depth, so a gap like that usually comes from the depth basis, a sloped floor or rounding.
Fill time assumes a hose that gives 5 US gallons a minute. That is a starting guess, so time how long your hose takes to fill a 5 gallon bucket for your own number.
| Rink (ft) | 3 in of water, fill time | 4 in of water, fill time |
|---|---|---|
| 20 × 40 | 1,496 gal 4 h 59 min |
1,995 gal 6 h 39 min |
| 24 × 48 | 2,154 gal 7 h 11 min |
2,873 gal 9 h 35 min |
| 30 × 60 | 3,366 gal 11 h 13 min |
4,488 gal 14 h 58 min |
| 40 × 80 | 5,984 gal 19 h 57 min |
7,979 gal 26 h 36 min |
| 50 × 100 | 9,351 gal 31 h 10 min |
12,468 gal 41 h 34 min |
Common sizes in meters
Fill time at 19 liters a minute, which is the same 5 US gallon guess.
| Rink (m) | 8 cm of water, fill time | 10 cm of water, fill time |
|---|---|---|
| 6 × 12 | 5,760 L 5 h 3 min |
7,200 L 6 h 19 min |
| 9 × 18 | 12,960 L 11 h 22 min |
16,200 L 14 h 13 min |
| 12 × 24 | 23,040 L 20 h 13 min |
28,800 L 25 h 16 min |
| 15 × 30 | 36,000 L 31 h 35 min |
45,000 L 39 h 28 min |
What a slope does to the number
Few yards are flat. The water surface stays level, so the shallow end sets the minimum and the low end fills deeper. A 30 by 60 ft rink with 3 in at the high end takes 3,366 gallons on level ground. Let the back end sit 6 in lower and it takes 6,732 gallons, with 9 in of water at the deep end. At 5 gallons a minute that is 22 h 26 min of hose time instead of 11 h 13 min.
For an uneven yard, measure the four corners and use the calculator. The sloped yard guide has board heights for each drop.
Notes on the numbers
- Your water bill or meter shows the real number. Many towns bill per cubic meter or per 1,000 gallons, so the tables help you guess the cost before you start.
- Water weighs about 8.34 lb per US gallon, so the 30 by 60 ft rink at 3 in holds about 14 short tons of water. The boards on the low side carry most of the push.
- Later top floods use far less water than the first fill. The flooding guide has gallons for thin layers.