air compressor lines.......again

[zzebby]

Yes we have all beat this to death I know.....but  I have a paint / dirty shop with roof only, no walls that is 110 feet from my main garage. Do not want two air compressors so an air line is the only way.  Different wrinkle here is that I will bury it underground.  Can't use black pipe or copper because of corrosion and copper is way too many $$$.  Leaves galvanized pipe or.........the taboo  PVC .  I think the safety issue is OK as it will be 18 inches underground and where it comes up I'll switch to steel.  It will also cool and so help dry the air with proper drain lines.  I'll have a ball valve where it leaves the garage and only have it on when needed,  painting or whatever out in the dirty shop.  Notice I'm in AZ  so no concern with freezing and little rain also.
Would you use PVC

[Bruce Dorsi]

Being buried 18", I think you will be safe.

However, I would opt for Schedule 80 PVC instead of the more common Schedule 40 PVC pipe.  .....The thicker walls increases its strength, and will provide a greater margin of safety.

I don't know what your soil is like, but it is probably worthwhile to lay the pipe on a bed of sand and cover it with more sand, before backfilling the trench.

The upper limit for fluid temperature for most PVC pipe appears to be 140  degrees.  ......As long as you're not putting very hot air from the compressor directly into the PVC, you should be OK.  ......The compressor tank should absorb most of the heat from the compressed air.

Another possibility that you could look into is using black polyethylene pipe.  .....This is usually sold in rolls, and would require fewer connections underground.  ......It is available in several Schedules, and is made of MDPE or HDPE (HIGH or MEDIUM Density Polyethylene).  ......The pressure rating of PE pipe is affected greatly by the temperature of the fluid.  .....The poly pipe may possibly be cheaper than the PVC.

[wayne petty]

http://www.harborfreight.com/cpi/ctaf/displayitem.taf?Itemnumber=30267

[zzebby]

Yes some good ideas.  Surprised at only $35  for 50 feet of what appears to be good hose.  Would it rot underground ?  Here we often have 120 degree days in the summer so not much safety factor on the 140 degree rated plastic pipe.  Any other ideas ?  Galvanized pipe would be $ and a job to lay,   but would it be good forever ??  Or still corrode underground ?

[enjenjo]

Dirt is a very good insulator, so 18" down, the soil temperature will be no where near air temp.The nice thing about polyethylene, it does not fail catastrophically, rather it balloons.

[Crosley.In.AZ]

I would use 1 inch  schedule 80 or40  PVC  and also have a storage tank in the shop so there is a larger volume there if needed for an air gun to blow off stuff.

Always primer  each joint on the PVC  before the glue is  applied

The tank may help to separate water out too.

[zzford]

I have my compressor out in my shed, about 20 feet from my garage. I too, used PVC pipe and buried it. That was about 7-8 years ago and no problems to report. It sure keeps the noise in the shop at a lower level. Now my wife can hear me curse when something doesn't go right.

[Harry]

Steel pipe would take more than 20 years to corrode. If at all.

[48ford]

I used pvc sch.80 in ohio,and use it summer and winter.
The compresser is 70-80 ft from the shop and is in the ground around 12'
I have used it for at least 15 years now.
But have you checked out PEX tubing?
They use this stuff in hot water heating systems,but I don't know how it holds up to pressure.
Just thinking here
Russ

[wayne petty]

Carlon Coil, 100 Ft., 3/4 In., Gray, Liquidtight Flexible Nonmetallic Conduit
Model # 15007-100    
home depot Store SKU# 233706    

i don't know if the 1/2 inch air hose will slip through this...

it's 51 bucks at home depot..

they might have larger diameters in the store...   or at electrical supply stores...

how much air in volume are you going to be using...  

how about one of the 5 to 7 gallon portable air tanks that you plug into the end of the hose when you are working out there... so you have a big reserve volume at the end and don't have to rely on the air flow through the hose to keep  up the volume for a short large use..

you might also want to check out the check valves that are used on truck air brake systems..  i was looking as  S S truck parts this morning..  they had several check valves... so there is no back flow possible..  you might also want to put a full flow to the atmosphere valve... so you can purge the line of any condensation once in a while..

just ideas...


pex tubing is an great idea also...

[Rrumbler]

You should not have corrosion problems in Tempe unless you have grass or trees around the line; good ol' "desert landscaping" probably won't hurt anything.  If you put in steel or black iron (same thing, basically) drive a ground rod at each end and bond the pipe to the ground rods and to your building ground rod.

[cr55]

PVC pipe is used for water and sanitary lines all the time buried underground without any problems. I think you'll be OK with it...CR

[jaybee]

You should not have corrosion problems in Tempe unless you have grass or trees around the line; good ol' "desert landscaping" probably won't hurt anything.  If you put in steel or black iron (same thing, basically) drive a ground rod at each end and bond the pipe to the ground rods and to your building ground rod.

Why the ground rod?

[Leon]

The warnings about PVC are about the way it fails IF it fails, and being buried removes the danger of flying pieces in the rare event it does fail.  I would think PVC would be the ideal choice for the underground portion of your line.

[Rrumbler]

Why the ground rod?

In the desert, a good ground is often a chancy thing at best.  Even though the pipe is buried, it will not necessarily contribute much to it's own grounding; driven ground rods six or eight (standard) feet long and placed at both ends of a pipe run, or along it at intervals of about fifty or so feet, driven to at least twelve inches below grade will add an element of safety that might be otherwise lacking.  An alternative would be to run a bare copper ground, #6 or 4 soft, along with the pipe in the trench, and bond the system that way.  Also, since the compressor will be in an outbuilding, the safety disconnect box should be grounded, but NOT BONDED TO THE NEUTRAL CONDUCTOR OF THE ELECTRICAL FEED; they should be isolated, that is, separated from each other, not connected together.  It wouldn't hurt to bond the tank of the compressor to the ground, either; it will help keep down the potential for electrolytic corrosion in the system.  Personally, if I were to use PVC, I'd run the wire, but with Iron/steel, the rods will do the trick, and are likely cheaper.

All this seems like overkill, but I have chased so many bad grounds on systems in this arid place, that overkill seems to be justified.  We could drive two eight foot rods down to nine feet, placed about six or eight feet apart in common desert soil, and a meg-ohmmeter across them would quite often read infinity; it should read SOME resistance, but not INF.  Just the observations of an old Desert Rat Electrician/Lineman.