How JustAnswer Works:
  • Ask an Expert
    Experts are full of valuable knowledge and are ready to help with any question. Credentials confirmed by a Fortune 500 verification firm.
  • Get a Professional Answer
    Via email, text message, or notification as you wait on our site.
    Ask follow up questions if you need to.
  • 100% Satisfaction Guarantee
    Rate the answer you receive.
Ask Phil Your Own Question
Phil
Phil , Mechanical Engineer
Category: Home Improvement
Satisfied Customers: 7485
Experience:  Retired contractor, 51 years experience
23932409
Type Your Home Improvement Question Here...
Phil is online now
A new question is answered every 9 seconds

what is the formula for calculating the amount of water collectible

Resolved Question:

what is the formula for calculating the amount of water collectible from annual rainfall off a flat surface (roof)
Submitted: 3 years ago.
Category: Home Improvement
Expert:  Phil replied 3 years ago.

Welcome to Just Answer!

The formula is:

H is the published annual rainfall height in inches and A is the collection area in square feet, the amount in gallons is given by

 

(H/12) * A * 7.48052 = gallons collected per year,

 

(thanks to some coaching from one of our masters degree physics teachers)

 

We must subtract from that figure however depending on the rate of rain fall per event and wind conditions, which will evaporate small amounts of water from a roof that would not evaporate from a rain gage.

 

a 10% to 15% figure would be a reasonable estimate of loss due to evaporation.

 

 




. I hold questions open after positive ratings to allow for unlimited follow up. Please be patient though. The research & typing take time.

Please rate positively, Thanks!

Phil

Phil and other Home Improvement Specialists are ready to help you