SPRINKLER TALK FORUM - You Got Questions, We've Got Answers

Just out of curiosity, how did you measure the pressure at the end of the drip tube? I haven't seen that done.

The only pertinent information I could gleam from a quick review of drip irrigation design at www.irrigationtutorials.com was that the total length of the drip tubing from the point water enters the tubing to the farthest emitter should not be more than 200 feet. Is specifically indicates that adding branches is ok but that the total distance isn't more than 200 feet (so as an example, you could have 400 feet of drip tubing IF the water source connects to the drip tubing at the center). But that doesn't address the issue of pressure loss possibly caused by lots of emitters. The only thing addressed about that is limiting the emitters PER VALVE. But his numbers work out to saying you should limit the system to what is equivalent to 10 gpm. But if you have 10 gpm feeding the start of a 1/2" drip tube, you are going to run out of pressure (so the 10 gpm rule seems to be what to limit an entire circuit likely feeding several 1/2" drip tubes with a 1" or 3/4" pvc).

However, many drip irrigation emitters are (at least some what) pressure compensating. That way, as pressure drops though the tubing (because of distance, friction losses, or hills), the emitters all still release about the same amount of water.

While not explicitly stated at the irrigation web site, I would gleam from other comments I could find that 15psi ios the lower end you would expect to see the water pressure. So 5psi does seem to be a bit low. The person to really take this up with is the ones that designed and installed the system. But before you do that, try testing the emitters and see if it's really making a difference. If you can, put an emitter near the start of the pipe over a pie plate (or any type of catch basin) as well as the last emitter closest to the point you are reading 5psi. If after operating the system for 20 minutes, there is less than a 25% difference between the two, I wouldn't worry about it too much. If there is a 50% difference, then IMHO you have a legitimate beef.

The other thing to try (if possible) is to test the pressure at the START of the line. If the pressure is significantly higher at the start, it might be simply a kinked section of drip tubing.

Thanks for the picture. I guess I misunderstood what you were saying. I thought you said the pressure at the end of the spaghetti tubing (1/4" line) was 5 lbs.