Air compressor for winterizing inground sprinklers

Posted by Stuart Benoff on October 21, 2005, 9:26 am

The sprinkler company says that it takes between 10 and 25 CFM to
properly blow out the sprinkler lines. I have a 4 gallon/125psi
compressor but the specs don't include it's CFM rating. Anyone know
what it is for this compressor or how to calculate it?

Thank you.

Posted by on October 21, 2005, 7:08 am

"The sprinkler company says that it takes between 10 and 25 CFM to
properly blow out the sprinkler lines. I have a 4 gallon/125psi
compressor but the specs don't include it's CFM rating. Anyone know
what it is for this compressor or how to calculate it? "

That is a basic compressor spec and should be on the compressor, in the
manual, or at the manufacturer's website. Failing that, take a look
online at similar compressors and you will get an idea of the possible
CFM range. A compressor the size you' re talking about is not going
to be anywhere near 10-25 CFM.

I blow my system out with an old Sears one that puts out 6.6 CFM at 40
PSI, with maybe a 10 gallon tank. It's not ideal though. I go through
the zones twice. Each time I let the compressor build up to about 75
PSI, then turn on the zone. The compressor can't maintain that
pressure, so it starts dropping. But it does a good enough job.

Posted by Stuart Benoff on October 21, 2005, 10:37 am

trader4@optonline.net wrote:

> "The sprinkler company says that it takes between 10 and 25 CFM to
> properly blow out the sprinkler lines. I have a 4 gallon/125psi
> compressor but the specs don't include it's CFM rating. Anyone know
> what it is for this compressor or how to calculate it? "
>
> That is a basic compressor spec and should be on the compressor, in the
> manual, or at the manufacturer's website. Failing that, take a look
> online at similar compressors and you will get an idea of the possible
> CFM range. A compressor the size you' re talking about is not going
> to be anywhere near 10-25 CFM.
>
> I blow my system out with an old Sears one that puts out 6.6 CFM at 40
> PSI, with maybe a 10 gallon tank. It's not ideal though. I go through
> the zones twice. Each time I let the compressor build up to about 75
> PSI, then turn on the zone. The compressor can't maintain that
> pressure, so it starts dropping. But it does a good enough job.
>

I was thinking that it should be a "basic" spec but I can't find it
anywhere (manual, compressor or the website). It's a Husky FP2021 and I
bought it from Home Depot.

Thanks for your help.

Posted by chocolatemalt on October 21, 2005, 1:51 pm

> trader4@optonline.net wrote:

> > "The sprinkler company says that it takes between 10 and 25 CFM to
> > properly blow out the sprinkler lines. I have a 4 gallon/125psi
> > compressor but the specs don't include it's CFM rating. Anyone know
> > what it is for this compressor or how to calculate it? "
> >
> > That is a basic compressor spec and should be on the compressor, in the
> > manual, or at the manufacturer's website. Failing that, take a look
> > online at similar compressors and you will get an idea of the possible
> > CFM range. A compressor the size you' re talking about is not going
> > to be anywhere near 10-25 CFM.
> >
> > I blow my system out with an old Sears one that puts out 6.6 CFM at 40
> > PSI, with maybe a 10 gallon tank. It's not ideal though. I go through
> > the zones twice. Each time I let the compressor build up to about 75
> > PSI, then turn on the zone. The compressor can't maintain that
> > pressure, so it starts dropping. But it does a good enough job.
> >

>
> I was thinking that it should be a "basic" spec but I can't find it
> anywhere (manual, compressor or the website). It's a Husky FP2021 and I
> bought it from Home Depot.
>
> Thanks for your help.

Indeed it seems the CFM and pressure output numbers for that compressor
are nowhere to be found -- probably because they're horrible. But it's
just a small portable unit so that's understandable.

Likewise, I have a portable Porter Cable compressor that seems nice and
solid and delivers 6 CFM @ 90 PSI, but it's inadequate for blowing out
sprinklers. Like trader4's experience, I can let it build up pressure
then try to "surprise" the zone with a fresh blast of air, but it's gone
in a few seconds and the motor is chugging along while the heads are
blowing out a little air and no water. So I disconnect and wait for a
re-pressurization for the next "surprise". With 2 or 3 interations per
zone, the heads seem to get cleared. Concerned about the 50% duty cycle
of the unit and not too keen on burning out the motor, I give it 10
minutes on and 10 off... and it takes at least an hour and a half of
tedium to blow out 8 zones. I'm not sure if I'll slog through it again
this year or pay $20-30 for the pros on the truck.

I suspect you really need a $500-$1000 compressor to really get the job
done, i.e. one of those hot-water-heater-sized monsters.

Posted by Stuart Benoff on October 21, 2005, 4:17 pm

chocolatemalt wrote:

>
>

>>trader4@optonline.net wrote:

>>>"The sprinkler company says that it takes between 10 and 25 CFM to
>>>properly blow out the sprinkler lines. I have a 4 gallon/125psi
>>>compressor but the specs don't include it's CFM rating. Anyone know
>>>what it is for this compressor or how to calculate it? "
>>>That is a basic compressor spec and should be on the compressor, in the
>>>manual, or at the manufacturer's website. Failing that, take a look
>>>online at similar compressors and you will get an idea of the possible
>>>CFM range. A compressor the size you' re talking about is not going
>>>to be anywhere near 10-25 CFM.
>>>I blow my system out with an old Sears one that puts out 6.6 CFM at 40
>>>PSI, with maybe a 10 gallon tank. It's not ideal though. I go through
>>>the zones twice. Each time I let the compressor build up to about 75
>>>PSI, then turn on the zone. The compressor can't maintain that
>>>pressure, so it starts dropping. But it does a good enough job.

>>I was thinking that it should be a "basic" spec but I can't find it
>>anywhere (manual, compressor or the website). It's a Husky FP2021 and I
>>bought it from Home Depot.
>>Thanks for your help.

>
>
> Indeed it seems the CFM and pressure output numbers for that compressor
> are nowhere to be found -- probably because they're horrible. But it's
> just a small portable unit so that's understandable.
>
> Likewise, I have a portable Porter Cable compressor that seems nice and
> solid and delivers 6 CFM @ 90 PSI, but it's inadequate for blowing out
> sprinklers. Like trader4's experience, I can let it build up pressure
> then try to "surprise" the zone with a fresh blast of air, but it's gone
> in a few seconds and the motor is chugging along while the heads are
> blowing out a little air and no water. So I disconnect and wait for a
> re-pressurization for the next "surprise". With 2 or 3 interations per
> zone, the heads seem to get cleared. Concerned about the 50% duty cycle
> of the unit and not too keen on burning out the motor, I give it 10
> minutes on and 10 off... and it takes at least an hour and a half of
> tedium to blow out 8 zones. I'm not sure if I'll slog through it again
> this year or pay $20-30 for the pros on the truck.
>
> I suspect you really need a $500-$1000 compressor to really get the job
> done, i.e. one of those hot-water-heater-sized monsters.

Thanks for the feedback. I guess it's the distance of the sprinkler
lines that makes the difference because this compressor was good enough
to blow out the lines in my inground pool (well, at least I think it was
but won't know for sure until I try to open it next spring). And, for
the record, they charge about $65 in my area to blow out the sprinkler
lines.

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