View Full Version : What size air compressor is necessary?

09-20-2005, 05:09 PM
I need to blow out the sprinkler system for the Winter.
I live in NJ and heard it need 150 psi compressor.
I read somewhere else I need 40psi and 10 cfm?
Any affordable compressors for under $400?
Thanks in advance.

09-20-2005, 05:33 PM
This is my second winter in an area requiring that same service. I find that a $30.00 visit/year from my landscape company is a lot cheaper than buying a new compressor plus fittings plus lugging hoses to the manifold..........

09-20-2005, 05:38 PM
It seems 150 would be too high, because you risk blowing off the heads. Out here we don't have to do this, but it seems to me that 40PSI/10CFM would be more than adequate to get most of the water out of a system.

09-20-2005, 06:28 PM
I agree with JIMBO.
Can you put a bubble of air an the system and then open one head at a time?

09-20-2005, 06:42 PM
The compressor I use for winterizing and testing is a Sears Craftsman 3gallon 1.5 hp 150psi max(?). The tank is hot dog style,which I think was discontinued and replaced with a pancake style (2hp,4gal). I think they are around $200.00.

I only winterize a couple of systems a year and yes I need all of the psi and at times a bigger tank. Definately need the pressure to push that water an open the heads as some of the heads are on long runs.

09-20-2005, 07:29 PM
I blow out my system every year with my 5hp 20 gal compressor. It takes about an hour to do 8 zones because the compressor has to recover and refill the tank after every zone. I set the pressure on about 60 psi with good results. You could do it with a smaller compressor but it would take a little longer to complete. I usually do each zone twice to make sure that they are all cleaned out. A professional usually uses a much bigger compressor because they can't spend so much time at each house doing the job.

09-20-2005, 07:43 PM
This is my second winter in an area requiring that same service. I find that a $30.00 visit/year from my landscape company is a lot cheaper than buying a new compressor plus fittings plus lugging hoses to the manifold..........

Good Idea! My compressor is not big enough to do it on a daily basis. But, if I got a lot of calls for it.... I would probably sub it out instead of investing in and transporting a large compressor.

10-12-2005, 12:21 PM
Where do you normally put the air to blow the system?
I just bought a compressor for some air tools so figured I'd do it. Last years in house didn't do it but had a couple of frozen heads break.
I guess I'm asking how do you do it?

10-12-2005, 01:01 PM
Depends on what is available, or not available, and how your system is layed out. If you have a hose connection, on each zone, you can put together an adapter to connect there.

If there is no hose bibs available you are going to have to find a way to break into the supply line and attach the compressor there (with a water shutoff before). I use quick connects on the air hoses which makes it easy to connect.

I would also suggest you limit your output pressure to around 50 pounds or so. I blow out each zone several times as you will probably go through your air quickly to the point of not being able to maintain 50 pounds (shut the zone down and let the pressure rebuild). You can control each zone either by your controller or manually at each valve.

Hope this helps a bit.


10-18-2005, 12:01 PM
After all the back and forth.... you guys convinced me.... Went out this morning and bought 3 fittings to adapt to my system... Blew it out with my 5gallon, 135psi compressor system designed for nail guns. Set the regulator on 70psi and went to town. Blew each zone with one "tankful", allowing the compressor to recharge fully between blows. Did each zone twice.... and it seems to have worked beautifully. $10 worth of fittings plus my labor (which my wife tells me is free) - beats the $50 I would normally pay...

10-18-2005, 02:00 PM
Where did you put the fittings. The on/off valve for my sprinklers is about 4 feet under ground, turned with key on long pipe handle. then it comes up and makes 90deg turn in a box. Maybe there's a place to hook up there. I"ll look.

10-18-2005, 04:09 PM
I have a regular faucet inside my basement on a drop leg that leads to the outside pipes. Hooked up there, isolated the house pipes with the valve that leads there, opened the drop leg valve - then opened each zone individually as the compressor recharged.

10-19-2005, 10:30 AM
INteresting, wonder if there's a reason not to use the outside hose bib that can be isolated from the house that is hooked between the house valve and the street (city supply valve)?
I want to avoid putting in some new fittings if possible.

10-19-2005, 01:26 PM
Sounds like (here comes a dangerous assumption) your best spot would be after the shutoff valve and before the pipes go into the zone valve box. I would put a hose bib at that 90, allowing me to isolate the sprinkler system with the existing shut off valve and blow it out through the new hose bib. Unfortunately, that will leave water between the old shut off valve and the new hose bib - but you indicate that's underground. Here in this area of Colorado I don't think (here's the dangerous assumption part) you would have to worry about the buried pipe. You'll note I'm right up I-25 from you.

09-22-2006, 06:27 PM
I wanted to know what size compressor to use. I eventually bought a sears
30 gallon and did each zone a couple times. I used schedule 40 pvc. I understand that the black plastic pipe in a roll that they sell for this purpose is better to use than the ridgid pvc. I would even think a smaller compressor would do the job just fine.

09-18-2009, 12:18 AM
The simple but sometimes hard to find adaptor to connect air compressors to sprinkler systems or faucets can be found here (http://lawn-aerator-attachment.com/air_compressor_to_garden_hose_adapter.html). You can download printer-friendly instructions on how to winterize various sprinkler systems here (http://lawn-aerator-attachment.com/Winterize%20Backflow%20Prevention%20Assembly%20and %20Sprinkler%20Information.pdf). Good luck!

09-25-2009, 09:41 AM
Do not use those what you call "ports" to blow air through the system. Those "ports" are test cocks, for a Cross Connection Device Inspector to test and certify the device. You will damage the device and it will no longer protect against backflow if you keep blowing air through it like that. I have seen many damaged RPZ's where a home owner thought they could save a few bucks and do exactly like you posted.

Below is a picture of what you are talking about, they are turn ball valve that are installed in the device to test the unit. There should be a total of 4 of them on an RPZ assembly.

10-09-2009, 10:54 AM
I have a 5-gallon 130 psi compressor I use for nail guns etc.

I understand all those issues of professional air compressors psi and CFM (Volume matters b/c time is money for professional landscapers) but I am in no hurry as a home owner.

This is what I plan to do:

- Fully charge Air Compressor
- Set Regulator to 60-70 psi.
- Bleed One Zone at a time.
- Let the Air Compressor fully "recover" before next bleed.

Any advices?

10-20-2009, 07:04 AM
I understand the CFM issue that commercial lawn service uses to bleed 99% of the water out of the sprinkler system, but read on...

1. Water expands about 9% in volume when frozen:

2. If you use a "Home" compressor like this 6-gallon 5 CFM Air Compressor:


I understand that using a "Home" Compressor like this: it is not a complete evacuation of water so some 50% of the water stays at the bottom of the the Black Polyethylene Pipe in the winter. Even when frozen, the water expands a bit but no big deal, there is air above it to expand:


My neighbor does exactly this (using a 6-gallon Air Compressor) and has never had any issues in the last 10 years.

Any thoughts/advices using the "Home" Air Compressor?

PS: My Sprinkler System is: Copper Pipe from House to Underground, then White PVC Pipe to Valves Box, then Black Polyethylene Pipe to Sprinkler Heads.
I understand that PVC Pipe is hard and more prone to freeze damage than Black Polyethylene Pipe, but the PVC Pipe is a short run from the Underground to the Valves Box.


10-23-2009, 05:10 PM
:mad:I installed new spriklers in my yard using a design from rainbird.com. My well produces 9 GPM with 50 PSI. I followed instructions from rainbird design, replaced the nozzles according to instructions and created 4 zones with 5 to 6 sprinklers each. None of the zones have more than 7 GPM. When I tested each zone everything worked as expected. I installed a timer but I have this problem: 50% of the time the sprinkler will not come up all the way. I have the same issue on all 4 zones, but as I said it happens 50 % of the time. I realized that if I manually open the valves twice everything is fine and the sprinklers come up fine. It seems to be an issue with the pressure (not sure, could be flow issue). I adjusted the pressure in my pump sta-rite sle 1 HP but I still have the same problem. If I use the timer some sprinkler won't come up and therefore won't work properly. It works fine if I open each zone by hand two time. How can I take care of this problem. Did somebody have this problem before? Thanks in advance.