Irrigation – Master Valves and Flow Sensors

[Dustin Maxam, RLA]

Hi Land8,  I am designing an irrigation system for a public park and streetscape and could use some input on master valves and flow sensors . Here is the run down:

• (1) 4″ Recycled Water Main POC w/ booster and wye strainer
• This supplies looped main at park and (2) legs of main for streetscape (1 mile).
• (5) controllers connected to supply main. (not 2-wire, city wants Irritrol MC-Es each independent)

With this in mind, here are a couple of questions:

1. Should Each controller to have a flow sensor and master valve at it’s sub POC?
2. If so, should we add an additional Normally Open Master Valve w/ High Low Flow sensors just after the 4″ POC to cut off the entire system?  Not sure how this would work without a controller and mandated watering window?
3. OR, is it better to run multiple parallel mains to each POC?  This seems to exacerbate the problem of a main breaking and there is still the problem of the needing a master valve and flow sensor just after the 4″ POC.

I am talking with Irrigation Reps. but I thought I would tap into the Land8 knowledge base too.  I would like to see model technical discussions here! Thanks.

[Tyson Carroll]

Talk about making a complicated system even more complicated. Just out of curiosity why does your city not want 2 wire systems? 

1. Yes but that depends on where your booster pumps is located in relationship to the sub POC’s. You also might look into hydrometers in lieu of flow sensor master valves. They are more expensive but are an all in one item and saves cost in labor and layout. 

2. You would have to have another controller in order to shut off the system. 

3. That is the route you will need to go depending on your answer to question 1. 

The issue you are going to have with the parameters that you have been given is that it has been made a greater possibility that there will be cross programming on the controllers and multiple systems will try to run at the system time or on the other hand a break could occur before your fs/mv causing greater issues. 

For each controller and mv you will have to set a high flow limit. That number will depend on your critical loss calcs and should be set not to exceed that amount. The controllers will also need to be able to communicate to a central and be programmed so that maintenance contractors do not have the ability to adjust the controllers. Communication to a central is needed to controllers are programmed to work together not against each other. 

Truth be told the simplest and cheaper method would to go to a 2-wire system. 

[Dustin Maxam, RLA]

Hi Tyson,

Thanks for the reply and info.  Yes, 2-wire or central control would be great and solve a lot of issues.  Just can’t get the old timers in this city on board with newer technology… Basically I have come to the same conclusion as you.  Have to design the system for worse case all (5) controllers running at the same time.  Need a dummy controller, w/ no stations, to cut off the whole system with a fs/mv.  However, I don’t feel this is necessary as someone will definitely notice a large main break!  I will do fs/mv at each sub poc/ controller and have to abandon the looped main in the park.

[Tyson Carroll]

Yes you would think that but a main line break at 1 in the morning may not get noticed until 7. 6 hours of a mainline break running is a lot of water at 4 inches. Plus 4″ mains are notorious for popping of using PVC connection. Steel fittings are highly recommended as are saddles at your valves. 

Whether or not you have tried it the city’s preferred system will required meter’s fs/mv, power, and controllers is going to cost at least $40,000 more than a two-wire system and that is not including the labor for the wiring. 

In thinking about it further you might need multiple booster pumps regardless depending your available PSI since the pump will need to be tied into the controller or tie a central controller to the bp to turn on during your water window. 

What your describing could be done for $13,000-14,000 with 2-wire. 

Good luck!

[Dustin Maxam, RLA]

Yeah, I agree – thanks for the fittings tip.  Rainbird and another booster pump designer are telling me we can use a variable speed/ freq. drive pump with a pressure switch and this won’t require a controller to fire the pump…  Hope that is true.

[Tyson Carroll]

As long as the pump can kick the system on and off w/o the controller you are ok. The downside of not having it tied to a controller is that if does not turn on there will be no alarm to communicate there is an issue. 

[Author]

Posts