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Drop in water pressure??


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Is it normal for the home to lose significant pressure when the Sprinkler system changes stations?

Normally I wouldn't find this because I'm out checking the heads as the unit cycles from one station to another.

However, last week the owner of a 1 year old home told me about this problem and I went in and ran the Kitchen sink fixture while I had the Sprinkler on Auto.

Sure enough, when the system changed stations the pressure dropped to nearly nothing as the stations switched.

This doesn't seem normal and I recommended further evaluation by a Plumbing contractor.

Would a pressure regulator on the main water supply line help?

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As Mark C. would say Depends.

It sounds like the main line is not adequate for the demand the system is placing on it. This condition will cause large fluctuations in the pressure. If the system is well designed, and shares the same meter/tap, there will be a drop in pressure when the system runs. You might see a momentary spike in pressure as the zones advance.

A poorly designed system can have large variations in the pressure.

A rotor zone should have a min. of 45 psi. The pressure is affected by the velocity of the water. Pipe sizing and proper demand rates will have an effect.[:-graduat

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In new construction in my area most of the sprinkler systems have there own supply line and meter coming from the street.

The added on systems are tied into the home supply will drop the water flow into the house when it comes on.

I would suggest getting its own supply line from the main line at the street supply line.

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Here most irrigation/sprinkler/drip systems are attached to the house water supply.

Black Jack is correct, when you see a big pressure loss it is commonly a big leak. Could be a pipe or at the valve box.

The other reason is the water supply is weak to begin with. I had one property where we installed a tank with a booster pump for the sprinkler system. It was a large home built in an old neighborhood where the pressure was about 45 PSI to start with.

Of course if this is the issue you will also have functional flow issues in the house as well.

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Could it not be a back flow issue? Once the new zone activates the lack of water in the piping for that zone may be siphoning water from the home, which is usually above grade. Any sudden redirection in pressure could change the pressure in the home, as there are usually not backflow devices or vacuum breakers installed in the home. Although this is probably not the cause, I had to add my two cents.

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1st. Thanks to everyone for your replies.

2nd. Thanks Charlie for the offer. I was headed out the door on my last reply and didn't see your offer until I got home later that afternoon. The offer was appreciated!

3rd. Chris, the drop in pressure is at all fixtures in the home, both hot and cold. I just used the Kitchen sink because it was closest and I could look out the window and watch the stations change and see the drop in pressure at the same time.

I've inspected 3 homes on this street, and all have this problem.

My theory is that the supply may be too small. Pressure is in the 55 psi range.

Yours?

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The other reason is the water supply is weak to begin with

Go with Scott's theory. I'd bet a steak at Disney the system shares a meter or the tap with the house meter. An irrigation meter (no matter separate or shared tap) has no sewer fee. The shared tap is less expensive from the city. 1 tap 1 fee 2 taps 2 fees. The system may even be on the same meter. A separate tap and meter draws on the city main (lots a water) and will not affect the water in the house.

Other things to look at:[:-magnify

GPM in each zone. Each head will have a nozzle size. Each manufacturer has a list of the flow rates for different pressures.

Main line size. Charts can be obtained for different types of pipe. The Rain Bird Catalog has these in the back. Class 160 or 200 is common the common PVC for irr in my market.

Think electricity. The bigger the wire (pipe) the more capability to carry amps(water).

1" class 160 PVC can carry 16 gpm, 3/4 10 gpm.

Determine the nozzle flow and you can see if the main is being pushed to hard. Increased water velocity drastically reduces pressure.

The differing "pressure" at the sink may show when low volume and high volume zones swap.

If the system has a backflow (it should) and you can take 8 - 15 lbs off of available water pressure. It depends on the design. Anyone want to buy a used backflow gauge? Our great state decided the Fed Clean Water Act did not apply to us.

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