Hi dreamngtree,

1. What is the volume of water you need to water your plants?
2. How high is the sources of water above your plants(height difference)?
3. How far (horizontal distance) is the source of water from you plants?
4. What is the flow from your source? Gallons per minute or how long does it take to fill a gallon or 5-gallon container?
You have a very interesting problem that may be looked at in various ways with the information provided. Aloha.

I would like to provide the plants with between 1/2 and 1 gallon of water per week. The water source is maybe about 5 feet higher than the plants and it is approximately 10 feet from the nearest plant and approximately 130 feet from the farthest plant and the lines travel along a continuous down slope. Raising the water source isn't really an option. I have the irrigation system setup with 1 GPH drip emitters off of 1/2 inch polytubing and/or 1/4 inch microtubing. I ran the system wide open (no valve) for about a hour and collected 1/3 gallon from one of the drip emitter furthest away from the water source. I can fill a gallon jug 2/3 full in less than five minutes at the water source. When I attached a battery operated valve, the flow was reduced to a trickle, and that valve requires a minimum of 10 PSI.

Any advice you can provide will be greatly appreciated.

You may be able to find a 12 or 24 volt solenoid valve, they are very common in turf irrigation systems and run off of clocks. Otherwise, try doing a web search for "actuated ball valves". I use them in our city's water system. They don't require any up or downstream pressure and should drop the inline pressure an insignificant amount. Our's are attached to timers that send a 24 volt current to the valve. Each foot of elevation gives you 0.433 PSI, so 5 X 0.433 = 2.17 psi, not much. I wish I knew more about your circumstances to offer some useful advice.

Hi dreamngtree,

great comment michael357.

There are battery operated solenoid valves run off 9V batteries attached to the house hose outlet. I have never had to operate a valve under very little pressure. Sounds like a little trial and error is needed. First your supply is only 8 gallons per hour, your system with emitters is set up for pressure operation. Low pressure systems need large piping to the plants. Small delivery systems increase the friction or decreases the pressure to the plants. You did not say how many plant you are watering. Under the current system you can only water about six plants at a time. The demand from your plants is greater than your source, illustrated by only getting 0.3 gal at the last plant instead of the rated one gallon. That can be solved by creating separate zones to be watered at separate time. You would need more valves, one for each zone. Three alternative come to mind.

1. Change emitters to smaller ones to bring total of emitter flow rate to match 85% of your source flow rate. Run system longer. Even have a slightly different rated emitters on the same line with the slower rated emitters in the beginning part of your irrigation line. This works because you have a downward slope along the plants. Trial and error to sort out even flow to the plants or increase water time for the lowest rated emitter. Check the flow from the first and last emitters.

2. Use hard (PVC) piping with hole drilled to each plant. Use 3/4 inch pipe. Trial and error again drill holes with different diameters with the smallest holes at the first plant to largest at the last plant. Start with small holes and slowly increase the diameters as you determine the pressure distribution of the PVC line. Your are doing physically what engineers do theoretically. You will be more accurate than the engineers.

3. Pressurize your system by having your source fill a tub or barrel with a small submersible electric sump pump(used for pond waterfalls, fairly inexpensive) connected to your irrigation system( on timer that matches your controller settings). The capacity of your storage should be large enough to deliver the water you would need for a week(can be greater). Automate filling the reservoir as well as the delivery system from the same Two Zone Controller. Keep the pressure around 20 psi with an in-line pressure regulator(inexpensive or get a 20 psi rated pump.

Of course, irrigation depends on the plants and soil porosity you are irrigating, one or two deep watering per week are better than many lights ones.

GL and Aloha

Search for "barrel drip emitter system" to read how to work with as little as 1 foot water head. Plus there is a battery powered valve that will work with "Zero Psi". You should use "flag emitters" so they can be cleaned often. Here are some - http://www.dripworksusa.com/emitters/_dta1.php -. Hope this helps.

Here is a link that might be useful: Some Emitters

Flag emitters didn't work at all for me (55 gal barrel, about 3 feet off the ground, furthest plant is maybe 15 feet from the barrel, using 1/4" tubing). Did they work for you?

I too have been looking at ways to use a rain barrel with some drip emitters (I prefer the adjustable ones).

I'm toying with a couple ideas.

1. Fill a 5 gallon bucket from the rain barrel and put a small submersible pump in the bucket to pump water into my drip line. These little aquarium pumps cost about $15, but shouldn't be run dry, so I'd have to watch the water level in the bucket. That would also allow me to apply liquid fertilizer (mix it in the bucket before pumping).

2. Pressurize my rain barrel. The two methods that come to mind are to do it manually by installing a hand pump from one of those pump, garden sprayers. Or, put a tire valve on it and use my automobile tire inflator.

Pressurizing the barrel seems to present the most challenges because all the holes in the barrel (screened downspout port, overflow port, etc.) would all need to be airtight.

Considering I already have a small aquarium pump and 5 gallon bucket, I think I might go that route and just make sure I don't run my pump dry (might use a timer or just trickle water from the barrel in to the bucket while the pump runs).

I built a system that also has close to 0 psi at the tank. I found a timer which has a ball valve and does not need any pressure to operate. So far it works great.

Here is a link that might be useful: Timer

Oh by the way I'm using 1/4" drip tubing with laserdrilled holes

Check with Home Depot. They have manual timers that water for given times. Spring regulator.
I don't know if they have a ball valve, but it may not matter.
If you are using a soker hose I think they have a pressure valve at the connection that will need to be removed. Check with Home Depot or someone that knows.

Karyl

Here is a link that might be useful: My Rain Barrels, Flicker

Check out the link to a rain barrel soaker hose test.

Here is a link that might be useful: Rain Barrel Soaker Hose Test

The only valves that work with near-zero pressure are servo-activated ball valves. These are ball valves that have little electric motors attached to the shaft and three wires.
When voltage is applied to one wire and a common the valve opens. When voltage is applied to the other wire and a common the valve closes.