Post date: Dec 17, 2014 3:05:42 AM
I plan to collect rainwater from the roof at one point. Maximum rainfall rate for Santa Fe is 2.2 inches per hour which translates to 1.371 gallon per hour per square foot or 0.0229 gallon per minute per square foot. For my 1200 sq ft roof, this is 27.5 gallon per minute, which can be handled by a 2” diameter vertical pipe with 3” diameter horizontal run.
Limit water build-up to 3” for normal 30 pounds per square foot (psf) roof load with scupper through parapet. (Just in case the drain gets plugged.)
The rainwater will be collected in a central roof drain - just like on an industrial building - which will be inside the structure where it will not freeze. A Zurn Z125 8” drain would suffice, which requires only an 11” hole for the deck plate, which is screwed to the roof structure. Roofing membrane is clamped to the drain with a collar. Or the insulation may be installed between the deck plate and the drain, using an adjustable extension to handle the thickness of the insulation.
The drain should be installed with a sump receiver (or ‘deck plate’) - a steel plate that ensures that the drain is below the roofing, to which the roofing is bonded and in which the drain is mounted. This can be mounted on top of the roof insulation because it spreads the load. Neoprene gasket (Neo-Loc) allows easy installation. Z125-NL (or -TC with Neo-Loc test cap) and 2” outlet.
Discard first few gallons of rain off the roof because it is dirty. A clever simple diverter is $25 and requires no vertical drop. Leaf diverters are also available from the same supplier. The diverter looks like the letter "T" with roof water entering on the left and clean water exiting on the right. The first gallon or so of dirty water drops into the vertical part, where it very slowly drains into the sewer. This vertical pipe could be made of clear PVC pipe to allow visual monitoring of the dirt removal. This dirty water can join the blackwater drain from the kitchen, along with the flush from the water softener, which is also in the garage.
The clean water flows into two 310 gallon (almost enough for 1” rainfall on 1,200 sq ft of roof area - 100 cu ft - 750 gallons) storage tanks for later distribution to garden. I had thought the rain barrels could be in the south corners of the garage, vertical. I’d prefer translucent (white) so I can see the water level. Each 310 gallon tank will weigh 2,400 pounds when full of water. This will require special reinforcement of the floor.
The stored rainwater will leave the bottom of the tanks. When the tanks are full, there will be enough pressure for drip irrigation, but when the water level is low they will need a small pump. This water exits through the south or west wall of the garage and will be used for drip irrigation.
The soil in this subdivision (Poganeab silty clay loam - see details below) is very limited for irrigation. Soil properties and qualities important in design and management of irrigation systems are
Soil properties and qualities that influence irrigation installation are
The properties and qualities that affect performance of the irrigation system are