My system came with a hose bibb directly after the PVB. I hook up my compressor to that for blow outs. I've seen people hook up to the test cocks too, but I've personally never tried.
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Here is my set up. Mainly just used spare fittings I had laying around.
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I am inclined to agree. However, I have sprinklers with the rainbird SAM check valves. I wasn't sure if that would present an issue or not. With that being said, here is where I got to this evening.Ware said:
I managed to hook it all up and use an undersized compressor to blow out the system.
The CFM of the compressor I have it about 4cfm. Based on how blowing out the lines went, if's time for a higher CFM compressor.
Any idea how to determine what size compressor is required? One website said take GPM and divive by 7.5 to come up with CFM, but that seems inaccurate. I can change nozzles on everything and dramatically change the GPM.
The CFM of the compressor I have it about 4cfm. Based on how blowing out the lines went, if's time for a higher CFM compressor.
Any idea how to determine what size compressor is required? One website said take GPM and divive by 7.5 to come up with CFM, but that seems inaccurate. I can change nozzles on everything and dramatically change the GPM.
I'm all for buying a bigger compressor (insert Tim Allen grunting) but hopefully it's not just for blowing out the irrigation. Changing your nozzle flow to flow less air won't help either. You want to push as much air as possible through the system. I'd be looking at options like hooking up an accumulator or surge tank to get a big temporary blast or renting a big compressor for a half-day or less to get the job done quickly.Movingshrub said:I managed to hook it all up and use an undersized compressor to blow out the system.
The CFM of the compressor I have it about 4cfm. Based on how blowing out the lines went, if's time for a higher CFM compressor.
Any idea how to determine what size compressor is required? One website said take GPM and divive by 7.5 to come up with CFM, but that seems inaccurate. I can change nozzles on everything and dramatically change the GPM.
For BIG systems, we hooked up a big 100-200hp diesel compressor and charged the system. Then opened the drain(s) sequentially and let 'er roar. Blowing through the heads is only necessary if you want to confirm the zone is dry or you know you have low spots in your piping that hold water.
That math is only correct for incompressible fluids. One cubic feet of water is 7.8 gallons of water. Air is a compressible.
The CFM needed will depend on your system/layout. For example, let assume your 1.25 in pipe is buried at 8in on a flat yard, but there is a section going underneath the sidewalk. This section goes down to 12in and then back up to 8in for each of the heads in the side walk.
When you first turn on the compressor and the pipe is full of water, it will push the water until there is a path for the air to go thru the pipe. Once the compressor airflow drops, it wont be able to push the water from the 12in deep section up to the 8in section and then up to the head. Water will likely travel back into the 12in section. You could recharge your tank and flow compress air again, but unless it has enough velocity and duration to lift the water from the 12in deep, water will remain in this section.
This is the best image I could find that shows what I mean (but think of it as a pipe in your yard).
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The water in the bottom of the left side of the image will remain there if there is not enough CFM to push it out. This water could freeze (if the ground temp drops below 32F at that depth).
The CFM needed will depend on your system/layout. For example, let assume your 1.25 in pipe is buried at 8in on a flat yard, but there is a section going underneath the sidewalk. This section goes down to 12in and then back up to 8in for each of the heads in the side walk.
When you first turn on the compressor and the pipe is full of water, it will push the water until there is a path for the air to go thru the pipe. Once the compressor airflow drops, it wont be able to push the water from the 12in deep section up to the 8in section and then up to the head. Water will likely travel back into the 12in section. You could recharge your tank and flow compress air again, but unless it has enough velocity and duration to lift the water from the 12in deep, water will remain in this section.
This is the best image I could find that shows what I mean (but think of it as a pipe in your yard).
The water in the bottom of the left side of the image will remain there if there is not enough CFM to push it out. This water could freeze (if the ground temp drops below 32F at that depth).
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