Draining the sprinkler system

[supton]

Ok, in typical fashion I left it for the last minute... I'm actually not that worried, one frost prediction for tonight and then it warms up again. All the same: I'm confused.

I've never had a sprinkler system, but I know it needs to be drained. So google to the rescue. All the info I come across talks about the anti-drainback valve on the outside of the house, with a pair of test ports. I don't have one, it seems. Inside the house there is a line off the water tank, a ball valve, then a simple one-way valve. Then the pipe goes up (I have a full basement), through the wall to the outdoors. Before it drops down to the ground there is a spigot. It then goes out to the control boxes where I see the valves for the seven zones (but no drain spigot). I don't see any fancy thing outside of the house.

I'm guessing I can hook up my air compressor to that spigot outside, select a zone, pressurize it to blow out the water, that seems simple enough. But am I missing something here?

 

[JohnnyJohnson]

Did you install it or have it installed? If someone that knew what they were doing installed it there should be some drains.

 

[wog]

You don t mention a bacflow device, so assuming you don t have one . You hook up compressor and blow out each zone one time and then go thru again. When no water is coming out your done.

 

[P10crew]

I am blowing mine out tomorrow

 

[walterjay]

Start with the closest zone and work your way out to the farthest zone.

 

[Rand]

you need quite abit of air a 100$ hf compressor wont cut it.

 

[Donald]

Originally Posted by Rand
you need quite abit of air a 100$ hf compressor wont cut it.


Not sure. I cannot believe the places that do it for customers bring out giant air compressors.

 

[Rand]

Originally Posted by Donald
Originally Posted by Rand
you need quite abit of air a 100$ hf compressor wont cut it.


Not sure. I cannot believe the places that do it for customers bring out giant air compressors.


This is a typical one you would see in a pickup truck
https://www.harborfreight.com/30-gal-420cc-Truck-Bed-Air-Compressor-EPA-III-62779.html

Air delivery: 18 SCFM @ 90 PSI, 19.5 SCFM @ 40 PSI

You can certainly do it "ok" with a lesser compressor.. just not a 5cfm 10 gallon $100 special.

Disclaimer: not an expert on sprinkler systems.

 

[A_Spruce]

If you don't have the capacity to winterize your sprinkler system, you may want to consider modifying your system to that end.

If you don't get hard freezing or frost below the top 3" or 4" of the ground surface, then your in ground stuff is fine, you only have to purge the water out of the above ground stuff. Not particularly hard to do, in fact, simply turning off the water to the system and opening the valve will put the water to ground level. If you can blow some air into the system to remove more water, even better. I've done this by lifting a pop-up and putting a clamp on the stem, then remove the emitter and blow air into the system there, this will force the water out the other emitters. Again, if you don't have a deep frost line, this will suffice. You then wrap the exposed inlet side of the valves.

If you get frost deeper than your system is buried, then you've got to get more of the water out, which will require plumbing in an air inlet forward of the shutoff valve, but before the exposed section of pipe leading to the sprinkler valve. With this air inlet, you can open the sprinkler valve and blow air through the entire system, but here's the catch, the more emitters on the line, the more CFM and pressure your compressor has to have to force the water out. You could cap all the emitters off between the valve and the end emitter, thus reducing the need to a very small CFM and compressor requirement. 4CFM at 50 psi with one inlet and one outlet can move the world, but that same input with 7 or 10 outlets (emitters) and that compressor won't have the nutz for the job.

FWIW, if your local hardware store doesn't have emitter caps for your brand of popup sprinkler, go to an irrigation supplier, they will.

 

[supton]

Hmm. Quick look shows my compressor is one of the small ones, like 4.3 SCFM at 90psi. I don't think it's many sprinkler heads per zone, but still. Might just be best if I pay to have it blown out.

It's NH, frost line is probably 3'. We routine go dig to 4' to prevent problems.

Sprinkler system came with the house, the name of the installer is on the setup, and even got a card in the mail from them about this job.

 

[Andrew1972]

Pay someone make sure you are home or work from home so that you observe the procedure and learn and ask questions.

 

[Astro14]

If they're coming to the house, I bet their compressor is no larger than yours. It's got to fit in the truck after all.

I would watch, see how they do it and then you're all set.

You've got to get most of the water out.

Not perfectly dry.

If they do, by chance, have a big compressor - well, how many services would it take to amortize your new compressor?

"Honey, I can save us money, but I need this new tool"...

 

[JustinH]

Pay the man and watch him do it one time.

 

[JHZR2]

Ive helped a friend drain his system using my portable 120v compressor... good for something like 4cfm.

Just go slow, ensure there's shut off valves between the compressor and the main, regulate it down, etc.

 

[supton]

I went and did it last weekend, double checked this weekend. I think my tank is undersized but it managed. I think as it heats up it slows down. Not sure about the short run of pipe from inside shutoff that goes through the wall to the outside spigot, as there is no way to drain it, but the system has been in place for years so

I left the spigot open.

 

[RhondaHonda]

supton-are you on well water? I know my municipality requires a backflow preventer and annual testing (scam) if you are on city water. It sounds like you don't have a back flow from your description. You got enough water out to be good for winter. The smaller compressors just take longer.

 

[supton]

Yes on a well.