Large System Water Pressure Discussion

[greenmonster304]

I guy I know does water main service line installs. Last year he had a commercial job installing a 4" fire sprinkler line and rpz. When the county came to test it failed the flow test. He sent a camera down the line line all the way to the county valve to look for obstructions. Then the county shut down the street line so the valve could be opened. They found that when the boys from the county did the wet tap they didn't cut all the way through and a piece was left in place and restricted the flow.
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[Sprinkus]

Originally Posted by greenmonster304

They found that when the boys from the county did the wet tap they didn't cut all the way through and a piece was left in place and restricted the flow.

I had one like that where the actual hole for the 2" tap was about the size of a finger. Seems that once the contractor doing the wet tap hit water he thought he was done.

I've done many wet taps through the years and always made measurements and marked the machine to make sure that I got the bit deep enough (without going through the other side of the pipe).

[Sprinkus]

Originally Posted by Irrigation Contractor

Several RB 5505 zones run #8 to #12 at 65-70 gpm and for this discussion we had 2 zones going at the same time. Meter A had static pressure of 91 psi and meter B has 49, but meter B was moving 10 gpm and A was ripping at 120 gpm.

Ok, so you're saying that these were static pressure readings, yet you're also saying that zones were running.
Have you mistakenly said "static" instead of "dynamic'?

What are the static pressure readings at meter A & B with no zones running?

[Irrigation Contractor]

Static Pressure readings on day of test:

Meter A = 91 psi
Meter B = 49 psi

Meter A and B share the same 4" mainline that is looped with 7 other water sources which scares the hell out of me which is why we have this Controller/System isolated to just run the 97 stations on a Tucor RKD.

We came into the project when it was about a 1/3 of the way completed and it was a total bastard child. The day we stepped onto the job the site was lacking water sources for what was already in the ground, then we started adding 70 - 100 zones a year.

Once the powers at be or check writers finally realized we knew what we were talking about they have been working with us to get everything right, yet they still do not like writing those checks. We isolated areas to avoid possible 500 - 600 gpm mainline breaks. LOL

[stebs]

Please tell us that this site doesnt have wells tied direct into the same mainline as city water...

[Irrigation Contractor]

I am definitely in agreement something is tapped wrong or closed off. We have dealt with several bad taps that were either not drilled all the way, the valves were partially closed and a couple where the plastic debris inserts were never removed after installation.

Static pressure should be the same through a pin hole or a 4" hole, but we are only getting a static reading at the backflow / meter. Since water is always running through the city lines is why I believe their is an issue with the water providers lines.

[Irrigation Contractor]

Originally Posted by stebs

Please tell us that this site doesnt have wells tied direct into the same mainline as city water...

That would be a NO.

[DanaMac]

I've mentioned it many times, I see a lot of PRVs go bad and restrict flow. We replace 5-10 a year due to this.

[cppendergrast]

In some cities with growing pains you will find high pressure mains along side low pressure mains. The low pressure mains serve the customers in that area and the high pressure mains are for distributing to the extremities of their service area. They do tap the wrong ones from time to time. That might explain the difference is static readings.

[1idejim]

Purchasing an non contact ultrasonic flow meter may help you to locate the restriction.
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