Drip Irrigation Issues

[iron]

I just installed some drip irrigation for some raised garden beds. I had 1-2 successful waterings, and 3 and counting unsuccessful ones.

The setup is as follows:
1. Spigot
2. Garden hose
3. 3/4" PVC, buried to beds
4. 3/4" PVC daylights and has transition from 3/4" to 1/2" poly tubing with threaded adapter
5. 1/2" https://www.amazon.com/Rain-Bird-SSF70-50S-Compensating-Sub-Surface/dp/B00VQC9MN2/ref=asc_df_B00VQC9MN2/?tag=hyprod-20&linkCode=df0&hvadid=193150648923&hvpos=1o4&hvnetw=g&hvrand=17164216170967971103&hvpone=&hvptwo=&hvqmt=&hvdev=c&hvdvcmdl=&hvlocint=&hvlocphy=9033271&hvtargid=pla-305160000939&psc=1 with some terminators at the ends

There are 4 runs of 50ft long tubing. The problem is that when water is on full bore, I get a hissing sound through the drip locations from air that's passing through. If I dial down the flow via a valve, the hissing goes away and the drip seems better, but not uniform (the holes that face down are better than the ones that face up). This doesn't seem right to me, but I'm not sure what could be different.

Thoughts?

 

[blades]

dial down your pressure its a DRIP system not a spray system. only need enough flow to get the whole thing leaking water.

 

[iron]

i had a pressure reducer on there per MFR recommendations (down to 25 PSI). still did it. not sure if i need to go more. but, if the holes in the tubes are facing up, then how will water ever come out of them?

 

[Ashful]

Two general thoughts, which may or may not have bearing on your situation:

1. Drip lines are usually intended for level runs, they don’t perform properly when one part of the run is lower or higher than another.

2. The 25 psi is at the line input, compensate for height if the pressure reducer is at a higher or lower location.

 

[zrock]

When i had the drip system i had the adjustable pressure reducer at the greenhouse and then each line had a valve on it. Once i got the pressure close then i adjusted each valve until the system was balanced.

 

[begreen]

1. Drip lines are usually intended for level runs, they don’t perform properly when one part of the run is lower or higher than another.

I haven't experienced that. How much elevation difference are we talking about? I have had multi-level Dripworks drip systems for a few beds for over 20 yrs.. Once the pressure equalizes in the tubes they drip at a consistent rate per the drip tape or drip line spec.. I also have a combo bed with drip line and some sprayers with a 3 ft difference in upper and lower beds. Works fine. In our upper garden there is about an 8' elevation difference between upper and lower rows. All the drip tapes are fed off of a 1/2" tubing header. I haven't put a measuring cup under an emitter to check flow, but I don't see evidence of the upper bed getting less water than the lower bed.

 

[iron]

my delta is about +1ft to -3ft from the spigot. we have high pressure and while i forget the flow rate, it was off the chart on the requirements for a rainbird sprinkler irrigation system.

 

[begreen]

i had a pressure reducer on there per MFR recommendations (down to 25 PSI). still did it. not sure if i need to go more. but, if the holes in the tubes are facing up, then how will water ever come out of them?

The drippers should have a pressure range and drip rate specification. The whole system pressurizes and then the drip emitter 'leaks' at the prescribed rate. Think of it as a hose under pressure that you poke a needle into. The hole is going to spray out because it's under pressure.

The bigger factor for sizing and output is length. Long runs will have greater resistance that needs to be compensated for.

 

[begreen]

@iron, the Rainbird product is new. I haven't used it, but in theory your setup should work. There should be a filter and a pressure regulator on the system at the spigot. If you open the end cap on a drip line do you get good flow out of it?

It could be that flow rate is inadequate and it is trying to feed too many feet (200'?) at once. Try plugging off a couple lines temporarily to see it that works better. If so, you may need to add valves to close off a section or two at a time. I have my main raised bed system zoned into 4 zones and water one zone at a time. That works quite well. It's on a Rainbird 4 zone timer that is connected to the underground pvc supply lines and uses Dripworks tubing in the beds.

This guide is helpful in designing a system.
https://www.dripworks.com/media/wysiwyg/drip-planning-guide.pdf

 

[begreen]

Another possibility is that an underground joint in the pvc blew apart. Do you hear a high rate of flow from the faucet?

 

[iron]

if a joint blew, i would see it given where in the yard i placed the pipe (poor draining soils). the underground run is <20ft and has a single bend. it daylights in the garden, then one line with a PVC valve goes to a strawberry bed. the PVC rounds a corner and then there are 2 tees and an elbow that all have male threaded ends for the drip lines to connect to. i need to take a picture...

 

[Ashful]

I haven't experienced that. How much elevation difference are we talking about?

The system that gave me trouble had 20 - 25 feet in elevation change from one end to the other. At 0.43 psi per ft, that’s an 8 - 10 psi drop at only 25 psi starting pressure. The lower emitters got all the water, the uphill ones barely emitted anything.

 

[begreen]

The system that gave me trouble had 20 - 25 feet in elevation change from one end to the other. At 0.43 psi per ft, that’s an 8 - 10 psi drop at only 25 psi starting pressure. The lower emitters got all the water, the uphill ones barely emitted anything.

Yes, that is a sizeable difference. It could be compensated for by zoning or maybe increasing supply tubing size to 3/4" the upper section?

 

[Highbeam]

I just put in a couple of zones of drip irrigation too and had a similar issue. On 1/2" line you are supposed to be able to feed 200 gph of emitters and 200' max line length. I was way over the 200 feet of length and the emitters were underfed as a result.

Don't worry about air in the line. It will all push out. Run times of hours are not uncommon with drip systems. After the zone turns off you will likely get all of the water draining out as the air reenters the lines. Incidentally, this is why backflow devices are required on irrigation and I didn't see one in your parts list.

Back to the OP, is the only problem air hissing that makes the watering events unsuccessful? It's okay to hear it.

 

[iron]

the problem is that ~half the holes don't drip.

i just talked with rainbird. apparently the holes need to be oriented facing sideways, not up or down or wherever.

i'll try this tweak when i get home tonight.

 

[Highbeam]

the problem is that ~half the holes don't drip.

i just talked with rainbird. apparently the holes need to be oriented facing sideways, not up or down or wherever.

i'll try this tweak when i get home tonight.

So we're dealing with drip line? Meaning every 9-12" you have a little 0.5-1 gph emitter in the tube? I did use 50' of that in 1/4". Was yours 1/2"? Still can't see why it matters as the air should just push out and water will come in behind it.

 

[iron]

So we're dealing with drip line? Meaning every 9-12" you have a little 0.5-1 gph emitter in the tube? I did use 50' of that in 1/4". Was yours 1/2"? Still can't see why it matters as the air should just push out and water will come in behind it.

see OP for product info

i would think air would be squeezed out too, but apparently it's not.

 

[begreen]

see OP for product info

i would think air would be squeezed out too, but apparently it's not.

That's kind of awkward. My Dripworks driplines (1/4" and 1/2") could care less about orientation. It's hard to control orientation when weaving around plants or circling trees. The built-in pressure compensating emitters should allow for consistent flow rates regardless of changes in pressure due to long rows or changes in terrain. Once the line is fully pressurized there should only be water in the line and the emitter orientation irrelevant.

 

[iron]

yeah, my thought too. it's not like irrigation installers are orienting tubing precisely. the product would go out of biz asap.

 

[begreen]

Was the support person in India?

 

[iron]

no, the guy's in the US, i believe. i've spoken to him before on another project. not very helpful and clearly not a troubleshooter.

 

[Ashful]

Yes, that is a sizeable difference. It could be compensated for by zoning or maybe increasing supply tubing size to 3/4" the upper section?

Yep, mine is all zoned out, now. The line size being too small will exacerbate pressure issue of regulator is at bottom of hill, and alleviate it if regulator is at top of hill. But if line is large enough to support given flow with minimal drop, it will have no bearing.

the problem is that ~half the holes don't drip.

i just talked with rainbird. apparently the holes need to be oriented facing sideways, not up or down or wherever.

i'll try this tweak when i get home tonight.

I have about a mile of this crap in 7 zones covering a half acre of gardens, and I’ve never heard of orientation of the holes mattering. Really, how would one maintain hole orientation in large installations? I think you got bad advice, there. What is your line size and maximum length on a single feed? What size is the supply line and well pump?

 

[Highbeam]

With 1/2” line being limited to 200 gph, each zone is only running at 3.25ish gpm. Hardly anything. A little 5/8 house meter will flow 15gpm. The real problem is regulating these things down to 25 psi and 1/2 tube. So little energy available to overcome the head loss.

 

[Ashful]

With 1/2” line being limited to 200 gph, each zone is only running at 3.25ish gpm. Hardly anything. A little 5/8 house meter will flow 15gpm. The real problem is regulating these things down to 25 psi and 1/2 tube. So little energy available to overcome the head loss.

Agreed. Moreover, the typical 1/2" drip line is rated around 0.9 GPH per emittter, and Rainbird puts their emitters on 40 cm (15.75 inch) spacings, so around 0.011 gal/min/ft. Lay out 200 feet of the stuff, and you're still only at 2.2 gal/minute. That's the draw of a typical sink faucet, this doesn't sound like a capacity issue.

I suspect the issue is just simply the use of the garden hose to feed it. 100 feet of 5/8" ID garden hose has a capacity of 1.6 gallons. Another 100 feet of 3/4" PVC has an additional capacity of 2.3 gallons. Maybe my assumed lengths are off, but either way, we are talking about a few gallons of air that must be pushed thru those emitters at a lowly 25 psi each time one disconnects/reconnects that hose, before the system is primed and flowing air at all emitters.

If half the emitters are seeing liquid, and only half air, it could take a few minutes to purge 4 gallons of air out of the system thru just 50 - 100 feet of emitters at 15.75 inch spacing.

A more typical system would have a permanent water hookup thru a vacuum breaker, and then valving close to the drip tubes, down stream of all that 3/4" PVC. This could be done with a regular PVC ball valve, if you don't want the expense of automatic valving, but this may be the whole issue.

Does the system eventually flow water out of all emitters, if left to run long enough?

 

[Highbeam]

Fascinating. I really don’t recommend vacuum breakers though. My current system uses a big fat brass double check valve that is much more flexible for installation and doesn’t introduce air.