Pressure Regulated Sprinkler heads


#1

I recently replaced all of my sprinkler heads with pressure regulated heads because I have pretty high water pressure. I ran into a problem I wasn’t expecting though. When I had the regular sprinkler heads all of the sprinklers were spraying a good amount of water from what I remember. Now though it looks like a sprinkler in each zone is not spraying much. Would changing to pressure regulated heads result in the available pressure dropping for the final sprinklers on the line? I was actually expecting the opposite, there would be more pressure available for each zone.


#2

@JPedrego

There is not a definitive answer because of a few factors. However, let’s troubleshoot and see what we can come up with.

Before you switched out your sprinkler heads were they emitting a misty spray accompanied by a hissing sound?


#3

Yes they were. I also know that the water pressure measured at 79 PSI at the inlet to my house


#4

Thanks. One possible solution is to alternate the pressure regulated heads with your standard heads. For longer lines I would use less regulated heads because the water needs to travel a greater distance, and having greater pressure can help.

Do you still have your old heads?


#5

Yes I do, although they are different brand then the ones I bought to replace them. Regarding length, there is one odd thing though. I was doing this for four of my zones with similar amount of heads. The two zones that are farthest away from the valves don’t have an issue though, all sprinklers are fully popping up and look to be spraying evenly.


#6

Wow! That is kooky.

Mixing the brands should be okay. For now, let’s try an experiment in which we alternate the valves in the two zones that are causing the most trouble.

Please let me know what happens.


#7

Ok, thanks, I’ll try that today when I get home.


#8

It is a shock for many people when they see a zone operating at the correct pressure because they are used to seeing mist. We recently retrofitted an entire median in Oklahoma City with 30 psi heads, plus removed the Rain Bird nozzles and replaced them with Toro Precision Nozzles. The gallons per minute dropped by 50 percent and the spray pattern is incredible. Bernoullis equation is interesting.
Take optimum 30 psi and divide by the measured pressure, then take the square root then -1. At Pressure of 98 psi then going to 30 psi, that is 38 percent drop in the gallons per minute.


#9

I don’t know about this. Think it better to have all heads pressure regulated. Maybe the issue here is undersized pipe and an issue of pure flow. He can take an inventory of the nozzles then look them up in the manufactures catalog. He can check the size of the pipe and look up pipe friction loss charts. Regarding flow, just had a situation where a site had 26 Rain Bird 8Van nozzles at 1.19 gpm each. Suggested swapping nozzle and the flow dropped to .20 gpm. Made all the difference in the world.


#10

If it was a flow rate issue wouldn’t I have seen issues with the unregulated heads as well though? Unfortunately I didn’t have the time to experiment with it today. Hopefully I can get to it tomorrow.


#11

What nozzles are you using?


#12

Rainbird u series nozzles on rainbird 1800 prs heads


#13

Those are good nozzles. As far as flow, if you have Class 200 PVC, check out the friction loss charts. Class 200 in 1 inch will flow 16 gallons per minute. 3/4 inch 8 gallons per minute. If you exceed this that could be your problem. Your 79 psi increases the gallons per minute, but destroys the nozzle spray pattern.


#14

I know I have 3/4 inch pipe. Not sure about the class. I’ll try to determine that. I added up the flow rate from the rainbird specification for each nozzle to determine the flow rate required for each zone. Looks like 6.47 gpm is needed for each zone.


#15

It will not matter with only 6.5 gpm. Class 200 is usually used on lateral lines and Scedule 40 for mainline, but this does differ according to your region. I find myself scratching my head on your situation. Could you have clogged filters? You could try flushing the line by removing one of the nozzles. Maybe you got dirt in the line when you changed out heads.


#16

That was it. I had to widen the holes for the new heads because the old heads were narrower. I guess I didn’t do a good enough job cleaning the hole out after digging it wider. The filters were very clogged. Thanks!


#17

Three cheers for @robertokc. The guy really knows his stuff !!


#18

Wow, that is so great. Glad the problem is solved.