Assuming a man is shaving his face and leaves the faucet running, and a woman is shaving her legs and leaves the shower running, we have:
We will assume that the face/neck effective shaving area is approximately 50 in^2
We will also assume that a leg has 2” radius and is 30” long. Effective shaving area of legs is therefore 2 legs x 2 x pi x 2” x 30” equals approximately 700 in^2 (rounded down to give the gals some benefit).
We will also assume that the effective shaving rate of face is 25 in^2/min., and that the effective shaving rate of legs is 50 in^2/min.
From Table E103.3(2) of FBC, Plumbing engineering, 2010, private lavatory flow rate is 0.7 gpm. Private shower head is 1.4 gpm. For purposes of energy analysis, we will assume that half of the flow is hot water, the other half is cold water.
1. Amount of water used to shave face = 50 in^2 / 25 in^2/min. x 0.7 gallons/min. = 1.4 gallons. Amount of hot water used is 0.7 gallons (50%, as per our assumption).
2. Amount of water used to shave legs = 700 in^2 / 50 in^2/min. x 1.4 gallons/min. = 19.6 gallons. Amount of hot water used is 9.8 gallons.
3. BTU for hot water for #1 above = 500 x 0.7 gallons x (120F-70F) = 17,500 BTU (equivalent to energy required to cool a single family home for an hour).
4. BTU for hot water for #2 above = 500 x 9.8 gallons x (120F-70F) = = 245,000 BTU (equivalent to energy required to cool a single family home for a day).
Total Water Used per Shave (gallons)
Hot Water Used per Shave (gallons)
Energy Used per Shave (BTU)
6. At Global Sanchez we do Plumbing engineering as well as other type of engineering in Tampa and Bradenton Florida. Our recommendations: all of us should turn off water when we don’t use it. This will save water and energy.