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ChrisDIY 08-16-2010 01:18 PM

Rain water collection system
 
1 Attachment(s)
I am thinking about building a large rain water collection system. I have created a sketch of what I am considering. See below. I am still trying to determine feasibility and practicality. To provide 1.5 inches of water per week to a 0.5 acre lawn in central Indiana from about mid June to Early September how much water would I need to retain? Is the amount unrealistic???

I would use one of the more advanced controllers that would use rain collection sensor and soil moisture to prevent it from using harvested rainwater until dry periods. The controller should be able to turn on the pump and incorporating a float switch should cut power to pump if water runs out.

What type of pump would I place in the "sump" to pump water into tank? I would need to make "quick connects" in order to remove all pump before winter. Our land is sloped enough to place sump and tank at least 1-2 feet below grade. Tank height I found was 97" and sump would be next to tank. Sump would have fine screen 30-45 degree angled lid. In theory rain water would flush off debris as it fills. Angle also would facilitate water getting to trench.

I have another downspout that is in a location where it is impractical to run gravity 4-6" PVC to a sump. Is there afloat activated pump that can pump from sump through 75-150 feet of 2-3" hose (PEX)

Provided tanks have knock out at bottom can connect same height tanks in series. Would just need to cut down and clear more land.

Expense may be so great I may just have to have a brown lawn...

EDIT: Using a calculation I found online and if I were able to use entire roof I can collect 30,000 to 35,000 gallons from April till September. I have found poly 10,000 gallon tank 12 feet wide 160 inches tall so would need to be able to pump to this height. No holds barred.

Conceivably could have a well water fill pipe with an "air gap" as back flow prevention since system will not be connected to homes plumbing directly.

Thinking...:whistling2:

AllanJ 08-16-2010 03:27 PM

So you are collecting the rain water first in a small tank (sump) below ground level and pumping it to a large tank (cistern) above ground level?

I think an ordinary sump pump will do.

I don't know what you mean by not using the harvested water until dry periods. If your well doesn't deliver enough water (gallons per minute) you cannot operate the sprinklers at all without using harvested wtaer. If your well can deliver enough water then you don't need this humongous water harvesting system.

ChrisDIY 08-16-2010 03:58 PM

Quote:

Originally Posted by AllanJ (Post 486864)
So you are collecting the rain water first in a small tank (sump) below ground level and pumping it to a large tank (cistern) above ground level?

I think an ordinary sump pump will do.

I don't know what you mean by not using the harvested water until dry periods. If your well doesn't deliver enough water (gallons per minute) you cannot operate the sprinklers at all without using harvested water. If your well can deliver enough water then you don't need this humongous water harvesting system.

After thinking more about where tanks would go (due to size and weight) I would need to put the sumps closer to the house and the tanks would be more than 200 feet away. Will post a picture from Google Earth. Tank(s) would still be adjacent to the yard. So my sumps would require a custom float and larger pump...:confused1:

ChrisDIY 08-16-2010 07:53 PM

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As promised Satellite image. The house has 4 downspouts. Two of which can be connected to gravity drains and ran to a "sump" which can then pump the water to the tanks. The green lines for sprinkler system is just for reference and by no means suggests a layout. Optional area to put tanks instead are #3 but would only be able to use downspout #2. Area #4 is the location which would allow sump to be right next to the tank however during the late fall and winter the tanks would be a lot more visible than sketched location. Downspout #1 should be able to have a simple 100 gallon rain barrel connected to a drip system and should work nicely for the future flower bed.

I am going to have the well cleaned and a draw down test done. If if is near the installation capacity from 2003, it may be a lot cheaper to install new well pump and upgrade the piping from the well to 1-1/4" up to the pressure tank. Are well pumps design to run for more than an hour 4 times a week?

For scale house is roughly 30 x 98

ChrisDIY 08-16-2010 10:44 PM

After looking at pumps the only way this would work is a sump and tanks at location #4.

In response to your question, I would take sump pump out late October early November when freezing temps are expected and reinstall early Spring. Hopefully, either the Rain Bird system with moisture sensor or a Davis Weather instrument system would keep the pump from running until late June. So the lawn would be watered by rain and not sprinkler system. My lawn was green up till about 3 weeks ago.

Scuba_Dave 08-16-2010 10:47 PM

Poly tank above ground could freeze
Mfg would need to tell you if it can tolerate freezeing

AllanJ 08-17-2010 10:49 AM

An ordinary sump pump can work if the total vertical rise is not too great (I think no more than 12 feet) and occurs first and then there is a downhill run the rest of the way (200 odd feet) to the large tank(s).

Otherwise you need a pump designed to move water significant distances.

ChrisDIY 08-17-2010 03:35 PM

1 Attachment(s)
Attached is the updated plan. The downspouts to PVC drain pipe need to go in even if I stop and go no further as I need to get the rainwater away from the house and beyond the berm. There are currently corrugated plastic pipe only extending 2-3 feet from house. I can add the sump and tanks at any time in the future as I have work to do. So will be looking for input along the way. I'll keep pics posted in showcase.

One major advantage to using this system vs. one involving the well is that all piping from well will need to run under the current and future deck expansion, under the future raised patio and also under the desperately needed retaining wall. This avoids it all together.


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