When my sprinklers come on, I lose regulation and I could use some help
diagnosing the problem.
My regulator is a Watts ND 35. The inlet pipe is 3/4". The regulator
adjusts the pressure, and seems fine. My sprinklers take 22 GPM because I
have 17 heads on one line. I know that's a lot, but I don't have much
choice at the moment. My sprinklers want 30 PSI. I have a hose nipple
right between my regulator and the sprinklers, so I attached my pressure
gauge there. If I adjust the regulator for 30 PSI when the sprinklers are
on, the pressure goes up to 65 psi when I turn the sprinklers off. If I set
the regulator for 50 psi, I don't have enough pressure to pop up the
Can I fix this problem by changing the regulator?
you need to size pipe correctly.
flow rate at what psi?
I use min 1" on iragation. sounds like you have not properly engineered the
system, a common mistake.
You are going to have to jack up the pressure because you have undersized
put a seperate pressure regulator on the line for house, let the iragation
get all the pressure it wants. (within reason).
I use the rpz backflow preventer for garden and a nd35 for the house.
What is the max psi for the iragation system?
why not let it max out?
Like Ned said, max out the pressure to compensate for the reduced flow in
the smaller pipe. On my home system I do not use a seperate regulator but
instead use valves with integrated regulators and backflow preventors (toro
valves can be seperated in the middle making replacement a simple task).
This way I can adjust the pressure on each branch seperately (some are drip
and some are spray).
Normally I don't bother measuring pressure, just adjust the regulator until
they pop up correctly. If you can't get enough pressure, you can reduce
the number of heads and buy longer throw, lower volume heads. I found that
the cheaper heads (orbit, rainbird) often would not pop up reliably but
better quality ones (toro) worked well (I don't know why since they look
very similar). Price was a good indicator of reliability on marginally
pressurized systems. If you have ample flow and pressure, almost any head
Mostly I am using 2", 3" popups, other styles and sizes may perform
differently than my comments.
? 4 Ned: does it make sense to use 1" irrigation pipe when all the pipe in
the house and main is 3/4" leading up to it. I used 3/4" irrigation and
have marginal flow now but after taking out a few feet of galvinized pipe
under the house last week and seeing what was inside, I am not surprised (at
least 50% volume reduction inside the pipe due to rust).
I never supply a house with 3/4" I use at least 1" on ALL water mains.
If all you have is 3/4" then you will not get any more volume at max psi by
putting 1" on the irrigation.
You will however be able to reduce the pressure in the 1" line. If you have
100 psi on the 3/4" line then you might only need the 30 psi in the 1"
I am starting to change my policy on well pumps. I am leaning toward soft
start continuous pressure pumps. they are GREAT for irrigation. They will
adjust rpm to compensate for pressure drop.
On city pressure (90 psi here) I only need pressure reg on house side 9 out
of 10 times.
I think it is rule or something.....to reduce pressure; increase pipe size.
if you had a 100 foot section of 3/4" pipe at 60 psi you would get 20gpm.
a 100 foot section of 1" at 60 psi would give you 38gpm.
so your setting of 50 psi is below the required 3/4 setting to get 22gpm.
even the 60 psi setting I show is still not quite enough. Like you say the
65 psi setting seems to work.
A 3/4" 100' line at 80 psi can deliver 24 gpm If I cut a tee in that line
and come off with 1" I can regulate the pressure down to just over 20 psi to
maintain the same gpm flow rate.
What you say makes a lot of sense. Maxing out for me means about 70
psi. I was told that you can begin breaking things at 80 psi anyway. I set
it up to 70 psi.
Please comment on the following:
All of this started because I have brown spots in the lawn. They are
generally about 3 ft from the sprinkler heads (12' or 15' heads). Sometimes
they are directly in ftont of a sprinkler. That made me think that I had
too much pressure and was spraying over the brown spots. I put out tuna
cans and confirmed that the brown spots are getting half as much water as
the green spots. That's when I noticed what my regulator was doing, and you
figured that out for me.
However, I still have the brown spot problem. My sprinkler coverage is
from head to head, and the dry spots are almost never at the outer edges of
a spray zone. The green spots are getting plenty of water and if I put down
enough water to satisfy the brown spots I will drown the rest of the lawn.
What could be causing this? Bad nozzles would seem to make sense, but
they are high-quality Rainbird (not Home Depot) nozzles and the spray looks
Do you have a dog? I bet it's a bitch. I have the exact same problem and it
is due to female dog urine. You almost have to follow the dog with a hose.
Try reseeding or sod patching with another kind of grass (If you can
tolerate the look). Inquire at local sod farms as to which grasses are most
tolerant of dog piss and your lighting conditions.
If you don't have a dog, maybe you are over fertilizing. In any case, I
really doubt it is a plumbing problem at this point. If the grass gets wet,
it gets wet. Try again in a lawn/gardening group.
If you want to additionally water your brown spots, try adding a drip
adapter under a pop up head and run a 1/4" tube to a low flow spray head.
You can position as many of these and move them around as needed. Total cost
$5 and negligable effect on presssure and flow to the other heads.
No, I don't have a dog.
I could be overfertilizing, but you may recall that I showed that I am
getting half the spray on the brown spots.
Oh, well, I will keep fighting the good fight. If I find a solution any
time soon, I will post it here. You have been helpful.
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