Advice Required Please, on pipe specs to reticulate the vacuum to the tool

**Redbog** · 10th August 2018, 07:41 PM

Hello All,

(Probably should address direct to Bob L,the family expert!).

My shed is now nearly complete, two halves, ( a"dirty"half for the saws, thicky, jointer, router), and a "cleaner"section for handwork, finishing, and some minor sanding.

I am trying to get things set up ready for retiring,( Hello Fletty), and have bought from a mate a 3 HP DC (6" outlets in "Y" configuration , for the lathe, jointer/thicknesser, Triton Router table, and small table saw). I also bought a 1 HP single phase dusty (4" dual outlet) for the"clean"side of shed. I have bought sufficient long radius bends, and blast gates and joiners, to send vacuum around the place. Maximum run from dusty to tool on either side is about 4M.

My query relates to piping the vacuum to the tool.

I fully understand, (40 yrs of it), pumping water, losing prime due to air on the suction side and so on, and the requirement for properly containing pressure on the discharge, esp in high head applications.What I don't know, is how vacuum behaves.

Specifically, would carefully sealed "storm-water" grade PVC be adequate, or does it need to be the much thicker "pressure" PVC? Would the vacuum of a 3 HP DC-suck "storm-water" PVC flat?

The price of "pressure"PVC in the larger diameters is scarey!

Any and all advice welcome!

Thanks everyone,cheers, Redbog (Harry).

**BobL** · 10th August 2018, 09:10 PM

Storm water ducting is fine - the vacuum pulled by conventional DCs is of the order of 10" of WC which is about 1/3 of a PSI. The pressure is all compression to which PVC is quite strong - even the thinner walled stuff like stormwater ducting.

Now lets talks about fittings.
The stormwater fittings tend to be lower quality and bends may have a tighter radius of curvature than DWV which is not good for air flow
For 90º bends I recommend the larger radius of curvature DWV bends and not the smaller radius stormwater bends.

good
Screen Shot 2018-08-13 at 3.11.31 am.png

bad
Screen Shot 2018-08-13 at 3.11.45 am.png

It doesn't look like much but the difference in flow rates is clearly measurable.

Check out these prices before you buy
Pipe Online - Retic Fittings , Plumbing Fittings, Reticulation Supplies supplied Australia wide
Some folks find that even with the expensive shipping their prices are hard to beat.

Don't sweat the "carefully sealed" - I don't seal many of my fittings as I invariable want to fiddle with the system too much.
I just push fit all the fittings ,and when required (ie vertical situations) add a small tek screw to hold it in place.

A couple of years back I was dismantling some 6" ducting and fittings at the mens shed that was about 3.5 above the floor ie I was up a tall ladder on one side of the ducting. I removed the tek screw but was having a devil of a time trying to get the fitting off the ducting. I belted and rocked and tried twisting the fitting without any luck. Eventually I belted it off with piece of wood and a mallet and then saw there was another tek screw on the other side that I must have put in during installation - this showed me that one screw was all that was needed.

**Redbog** · 14th August 2018, 01:13 PM

Good on you Bob, you have confirmed what I pretty much thought, but I don't know enough about vacuum behaviour. I thoroughlyagree about long radius bends, even in fluids, the short radius bends cause turbulence and lessen flow.

Cheers, Bob, hope you are well, adthanks again.

Redbog

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