sprinker blowout yourself questions

TimL(MI)October 4, 2004

I have searched the internet for two days for people who blow out their own sprinklers in the winter and what kind of compressor they use.. very vague or no answers at all..

Can anybody tell me if they blow out their own sprinklers and what size compressor they use?

Also, I was wondering if you could use a leaf blower to do it?

My leaf blower has 340 cfm/150 mph on high setting and

100mph on low setting(which is what I would try).

It seems that any homeowner sized air compressor wouldnt even come close to those cfm numbers.

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irri_guy(No CA)

Sorry, can't answer your actual question. You would laugh at what we call cold here.

I'm sure you need to give some idea of the size of the task, at least the pipe size of the largest sprinkler block.

I question whether a blower is able to produce adequate pressure to get the job done. I think you are after something like X cfm @ 40 psi.

Googled on "sprinkler blowout".

Part of what Colorado State Univ. says:

http://www.coopext.colostate.edu/TRA/PLANTS/index.html#http://www.colostate.edu/Depts/CoopExt/TRA/PLANTS/blowout.html

The most important thing to remember when "blowing out" your system for winterization is that air VOLUME and not air PRESSURE is the most critical element. If an insufficient volume of air is used, after having forced some water out, the air will ride over the top of the water. This will result in the remaining water draining into low spots and subjecting your system to freeze damage. Ideal pressures are in the range of 40 psi to 80 psi for the air compressor with 80 psi being the maximum.

Rule of Thumb: If the sprinkler heads stay up after the water is blown out, you are using the right size compressor.

The idea is to "blow" your system out using only the volume of air equivalent to the maximum gallons per minute (G.P.M.) for which your system is rated. In other words if you normally run one zone at a time when irrigating, you should blow out in the same way. If you try to do more, the excess velocity of flow and added friction will heat up the pipe and fittings to a point where they possibly could melt. If the pipe and fittings do not burst during this operation, they will be damaged and their life greatly reduced. As a result, failure will occur sometime in the future.

(Another site that seems authoritative is in the link. Note several important cautions there.)

Here is a link that might be useful: Winterblow

    Bookmark   October 4, 2004 at 10:59AM
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greenguy(Zone 5 OH)

i use a 5hp 30 gal compressor. it would really depend on your system and how many zones but you need a pretty good size tank to blow out a long run - even though you can do one zone at a time
if you do one zone at a time make sure you do them all at least twice

a leaf blower will not produce the pressure you need to push the water out

    Bookmark   October 12, 2004 at 6:04PM
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johnshenry

I was with you irr_guy until I go to this:

"If you try to do more, the excess velocity of flow and added friction will heat up the pipe and fittings to a point where they possibly could melt"

How does opening up more zones increase the velocity of air flow? And are you suggesting that air flow will cause heat build up and melt lines?

    Bookmark   November 8, 2004 at 1:00PM
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johnshenry

Ok, I see that you pasted that text from the CSU site irr-guy and it was not yours.

That really is a bunch of crap. Heat is a concern only if running the sprinkler heads bone dry for a long period of time. The mechanism MAY heat up and be damaged. But even if there is mist coming out, you are still wetting the gears and cooling them.

As for heat in the lines (mentioned in the article linked at the bottom of irr_guy's post), the compressed air will carry some heat, as it is natural for gases to be heated when compressed (and absorb heat when decompressed, that is how AC works). But the amount of heat for the pressures we are dealing with here is minimal, and not even close enough to melt pipe and fittings, especially those underground where heat is quickly conducted away by the soil.

I do auto restoration as a hobby and recently "upgraded" my compressor. I did very extensive research on psi vs. CFM, dual vs. single stage, pump margin fall-off, etc. I bought a 240 volt, 5hp 60 gallon compressor that is rated at 11.7 CFM at 125 PSI. Cost about $1000. Bottom line, is that any 10-25 CFM compressor will be huge. I am not totally convinced that that much air is truly needed. But my compressor worked well for the 8 zones I blew out yesterday, some with as many as 8-9 heads.

A leaf blower will never work, it all about CFM, but very low pressure.

A low end, single stage 120 volt compressor will clearly be better than nothing, but you will find the CFM outputs to be quite small. The size of the tank BTW, has nothing to do with the sustained CFM output of a compressor BTW. It is all a function of the pump and that is often directly related to the HP of the motor driving it.

JH

    Bookmark   November 8, 2004 at 1:24PM
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irri_guy(No CA)

"Sprinkler blowout" would get you funny looks here on the CA coast. We don't really know about hard freeze effects, although it stayed below 32°F for four days back in 1990. Busted pipe all over the region. Had no water at home for about last three days. Told ya you would laugh! I personally prefer to deal with fire, which I did in a prior decade.

    Bookmark   November 9, 2004 at 1:21AM
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deeproots(8b South Ga)

sprinkler blowout here means you didn't glue the pipe very well.

yeah heck, my well is sitting on top of the ground... pipe exposed and all, only once did it freeze enough to impede water flow.

dp

    Bookmark   November 9, 2004 at 1:18PM
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