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Harvesting Rainwater

S

sparkey

Active member
I am thinking of burying a 1000-1500 gallon tank and collecting rain water off my roof for my IBA rinse cycle. I know a few of you have discussed doing this before. Does anyone have any pros or cons to the results of collecting rain water that you would like to share?
 
These are excerpts from an article I wrote about rainwater several years ago.

“According to the experts, a one inch rain can produce over 500 gallons of water for every 1,000 square feet of surface area.”

1,500 SF and 30 inches of rain annually would have maximum yield of 22,500 gallons of water.

However, there are several issues to consider. The biggest is pattern of rainfall.

Where I live average annual rainfall is 45 inches. During rainy season, average monthly rainfall is six inches. However, this is slowest time for carwash. Thus, there would be times when 1,500 or 2,000 gallon storage tank would be filled. This would prevent further catchment of rain and the maximum potential yield.

In the spring, the busiest carwash season, average monthly rainfall is one inch. Sometimes during the spring, it may not rain for six to eight weeks. Thus, there will be times when storage tanks are bone dry.

“Can harvested rainwater be used to wash cars?

Rainwater is one of the cleanest water sources. It contains no sodium and being soft water it does not form scale or mineral deposits.

However, as rainfall comes in contact with the air, it dissolves naturally occurring carbon dioxide and nitrogen to form a weak acid. Moreover, a rainwater catchment area (roof) may contain dust, droppings from birds and small animals and plant and other debris. Consequently, rainwater needs to be filtered, disinfected and buffered before using it to wash cars.”
 
I have a different view-- it would only be enough water for 15-20 cars, at least with my vector over 100g a car.

Would it work better as an above ground tank to temper the water going to the auto, and save on presoak heat, or have warmer water to wash with. The dollarsavings on water might be too minimal unless you went up to 10 to 20k gallon
tank. The savings on heating may outweigh the water savings.
 
WOW,

You are missing the point.

Do the math. If fresh water cost $3.00 per 1,000 gallon, 22,500 gallons of collected rainwater “annually” would have a value of only $67.50.

Compare this to your water hog. 100 gallons a car times 20,000 washes annually equals 2.0 million gallons of water.

2.0 million gallons of water at $3.00/1,000 gallon would have a value of $6,000.

If you are paying more than $3.00/1,000 gallon, reclaim clearly makes more sense than rain harvesting.
 
I've done a couple of systems for marinas here in FL that have been cost effective. But that's because I used really big tanks, 5000 gallons, and they wash the boats all year.
 
This topic has been discussed here several times. I suggest that before you put any money into a system you find out if it is legal to harvest rainwater in your area since I understand that it is prohibited in some locations.
 
Depends on how you use. We have one tank and one pump. All guters, all weep and RO reject go to this system. Works fine and is very cost effective. We use for auto side rinse and undercarriage. I would agree that rainwater only would not be cost effective but if you combine with other sources the economy of scale works.

Ted
 
ted mcmeekin said:
Depends on how you use. We have one tank and one pump. All guters, all weep and RO reject go to this system. Works fine and is very cost effective. We use for auto side rinse and undercarriage. I would agree that rainwater only would not be cost effective but if you combine with other sources the economy of scale works.

Ted
Click to expand...

...and don't forget the marketing aspect.
 
Harvesting rainwater is not cost effective unless you have a BIG tank. I think the 22,000 gallons a year is probably about right with a smaller tank 1-2k gal. Factoring in time value of money, that is a never payback proposition.
 
Looks like this guy was doing more than collecting rainwater. He was diverting streams. To me that is a lot more than collecting rain water from your roof.
 
rph it does become a little murky. When I did the rainwater systems here in FL the state water management people told me that as long as we catch it before it hits the ground we can do anything we want with it. Once it hits the ground it belongs to them. This is kind of sad since most washes could cost effectively catch the storm water runoff in quantities that make it doable. You would have to clean it more, but you could collect tens of thousands of gallons worth.
 
Some times the laws do not make any sense. Here is Georgia you can drill into well water and use it to water your lawn but if you have a stream on your property and pump water out of it to water it is illegal.
 
Another issue is the sanitary sewer. You municipality doesn't likely have a way to measure effluent, so they base your sewer bill on water consumption. If you collect rain water and it ends up in the sanitary sewer, you would be in violation of the sewer use bylaw.
 
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