Marathon, FL rainwater: 31,570 gallons off a roof
Marathon, FL: gallons off the roof each year
31,570gallons a year
That is a 1,500 sq ft asphalt roof under Marathon, FL's normal 39.7 inches of rain, about 795 gallons for every inch that falls.
In Marathon, FL a single barrel does most of the work. Storms come often enough that a small tank refills before it runs dry, and a bigger one would mostly sit full.
Rainfall: NOAA 1991-2020 climate normals, the Marathon Ap station (1.7 mi away). Marathon, FL ranks 173rd wettest of the 173 cities covered in Florida.
Month by month in Marathon
| Month | Rain (in) | Off the roof (gal) | Garden shortfall (gal) |
|---|---|---|---|
| Jan | 1.64 | 1,303 | |
| Feb | 1.70 | 1,351 | |
| Mar | 1.33 | 1,057 | |
| Apr | 2.11 | 1,677 | 279 |
| May | 3.36 | 2,671 | 123 |
| Jun | 4.23 | 3,362 | 15 |
| Jul | 3.77 | 2,996 | 72 |
| Aug | 5.32 | 4,228 | |
| Sep | 6.37 | 5,063 | |
| Oct | 5.90 | 4,689 | |
| Nov | 1.79 | 1,423 | |
| Dec | 2.20 | 1,749 |
Sep is the wettest month (6.37 in, 5,063 gal off the roof); Mar the driest (1.33 in). Garden shortfall is what a 200 sq ft vegetable bed needs beyond the rain that lands on it, April to October.
What size rain barrel for Marathon
Best fit: 2 linked 55-gallon barrels, which delivers about 409 gallons to the garden in a normal year (83.5% of its need).
If you buy one, a 55-gallon barrel with a downspout diverter is the whole job. Check that the overflow points away from your foundation, because most of Marathon's roof water will pass straight through it.
| Tank | Water used (gal/yr) | Spills over (gal/yr) |
|---|---|---|
| 55 gal | 322 | 30,362 |
| 110 gal | 409 | 30,275 |
| 165 gal | 430 | 30,255 |
| 275 gal | 430 | 30,255 |
| 550 gal | 430 | 30,255 |
| 1,000 gal | 430 | 30,255 |
| 1,500 gal | 430 | 30,255 |
| 2,500 gal | 430 | 30,255 |
| 5,000 gal | 430 | 30,255 |
Simulated storm by storm through a normal year using the station's count of days with 0.1 in or more of rain each month.
Is rainwater collection legal in Florida?
Legal. Florida approves onsite non-potable use of rainwater for landscape irrigation, vehicle washing, filling pools and fountains and, in some local jurisdictions, toilet/urinal flushing (Florida Plumbing Code). No state storage cap or registration for non-potable collection.
Checked against the current source on 2026-11-06. Source