Gravity Fed Drip Irrigation - large setup

16 years ago

I'm in the middle of installing community garden.

The next step is to put in place a gravity-fed irrigation system.

The garden is about 30,000 sq ft with about 19,000 sq feet of it for gardening. The rest is landscaped for group activities and social. We've installed 800' of deer fencing and varmint fencing, rototilled several hundred yards of garden beds, and will start putting in plants in about a week.

For the irrigation side - I have on-site a 4,500 gallon plastic cistern and a 3,000 gallon plastic cistern.

The current plan is to harvest rainwater in the 3,000 gallon cistern off of a building roof that's about 500' away and periodically transfer the water to the 4,500 gallon reservioir cistern using hose and a pump. The local fire company will give us our first fill-up for the reservoir cistern.

I can pull about 1,000 gallons per inch of rain, more if I need to (by connecting into more of the building's downspouts)

The reservoir cistern is sited at the high point of the garden outside of the fence. It's about a four foot drop to garden beds which start 45-50' away. The garden itself has about a seven foot drop from the uphill fence to the downhill side of the fence across a distance of about 200'

The reservoir cistern is empty - I can put cribbing underneath it if I need to raise it to drive the gravity-fed irrigation . There's no electrity for the near future.

There are five distinct zones to the garden - colorscaped beds for community activies, communal vegetable rows for tomatoes, peppers, and such, private plot vegetables, youth gradening, and strawberry/ raspberry rows.

I have trades people involved who can drill holes in largish cisterns and put in the piping. They just need to know what to do.

If anybody can share some experiences with gravity fed irrigation what to do or what to avoid or can recommend a company to help with it, I'd deeply appreciate you sharing your thoughts.

Thanks,

Todd

ps. I've learned two things going through this proces -

1) rent a Dingo with rototiller and auger attachments at the start of the project, not midway through it.

2) take an ibuprofen before setting out to work on the garden

Sort by:Oldest

Comments (5)

lehua49
16 years ago
Todd,

Man you are doing the hard stuff. Two ibuprofen is better. Here is the hydraulics. Approximately 0.5 psi for every foot of elevation the water level is from the garden surface. For example if the height difference is 10 feet you will experience 5 psi at the garden outlet pipe. The pressure will decrease as the height of the water level decreases. In low pressure water distribution pipe sizes need to be bigger because your flow velocity will be low. See what flow your system will deliver by filling a 5 gallon bucket up and timing the fill. Do it several times and average the gallons per minute. You will now know how long it will take to deliver a certain amount of water to a zone. At least you won't need pressure regulators but probably a filter screen if your going with drip or soaker hoses. Think about pvc with holes drilled into it at what ever spacing you need(I can help you with this). You need to calculate the usage flow rate of the drip tubing or soaker hose to plan correctly for even distribution. Who will coordinate the water regime for the garden? Talk to a local landscaper to help you and you will advertise his name in the garden. Trial and error is a way of learning life. Aloha
thmcintyre
Original Author
16 years ago
Thanks for the insights - I like the idea of drilled PVC pipes rather than going with drip or soaker hoses.

I'll have more detailed plans tomorrow once I finish the sod-busting/rototilling and can take some accurate measurements.
Related Professionals
Richmond Landscape Architects & Landscape Designers · Vineland Landscape Architects & Landscape Designers · Annapolis Landscape Contractors · Kansas City Landscape Contractors · Raleigh Landscape Contractors · Georgetown Landscape Contractors · Chicago Landscape Contractors · Effingham Home Additions · Oxford Home Additions · Fall River Home Additions · Erie Home Additions · Bakersfield Home Additions · Clearlake Home Additions · Billings Home Additions · Yakima Home Additions
lehua49
16 years ago
Mc,

Less likely to clog over the long term. Aloha
jsnyd23
16 years ago
Not sure I agree with the idea of drilled holes in PVC. I think the best way to go would be using T-Tape. It works great at low pressures (like those found in a gravity fed system) and won't clog like you may experience with open holes in PVC. Lehua's approximation with .5psi per foot was very accurate, however for exact measurements it is 1 pound of pressure for every 2.3 feet of elevation. If you have a drawing of the garden you can submit it to Dripworks and they will design the system for free (no obligation to purchase). I think they even offer a 10% discount to community gardens.

Here is a link that might be useful: Free Drip Irrigation Design
lehua49
16 years ago
Js,

I am with you except drip lines with pressure compensated emitters have a history of clogging because of the torture track path the water has to travel through before exiting the emitter and not pristine municipal water. Otherwise the holes would be similar to drilled holes in PVC. The size of the holes is the key factor. The hole size should relate to the slope of the tube. This can be achieved by the trial and error method or calculated. Drip is already figured for you but you need the flow rates, pressure and slope to complete the design. One step at a time when gardeners are beginning to size up the situation. Whatever you feel comfortable with and gets the job done. I learned by trial and error and experimenting. Good Link but you might not want to give all the contact info required by the site to get the info. It is not hard to get the info other places. There are past thread experiments discussing these very systems. Aloha