Question on Piping

Question on Piping · 05-24-2009, 10:42 AM

I am in the slow process of installing a dust collector as funds are available. The DC will be going in the corner inside for now and later in another room. There is one problem I am not sure about, I plan on using thin wall white 4" pipe w/the fewest amount of flex possible. So now to my problem, where it is stationed in the corner there is a old cast iron vent pipe that was used for the bathroom when there was one in the shop. I need to run the line for the DC between the CI pipe and the wall except there is not quite enough room (I need an inch) . Will it be a problem to use fittings to go around the pipe or would it cause a problem to squeeze a short section of flex in between? Removing the CI pipe will be real tough as it goes through 2 sections of roofing at different levels and the lower one is NOT accessible.

So do I cut it out and seal it at the ceiling or can I go between the wall and the CI pipe? cutting it out will involve securing it first to the rafters with a bolt through it and then cut it into.

Mike Davis · 05-24-2009, 12:53 PM

Why not take out the old cast iron pipe completely?

Cut it off at the floor and plug it.

Alan in Little Washington · 05-24-2009, 01:47 PM

Put a bathroom back in the shop- an indispensable creature comfort in my shop- remove and re-plumb the CI vent stack in pvc and run it so it avoids where you want to run the DC duct. Depending on the size of your shop and your DC, you may want to consider 6" pvc ducting, anyway (now or later).

Dudelive · 05-24-2009, 02:03 PM

@Mike
That was my thought at first but I guess I am almost lazy. Seems like do it right the first time and I won't have to redo it later situation.

@Alan
Excellent idea except the shop is rather small as is now at 13+ X 18+ .,..Also the house is not that far although it is totally separate. It makes you be dang sure you don't need to go back in the house BEFORE you start a project.

So I just need to figure out the best way to plug both ends of the CI pipe after I figure out how to cut it. The sawzall might get to be used for this along with 3 - 4 blades.

Glennbear · 05-24-2009, 02:29 PM

Originally Posted by Dudelive

@Mike
That was my thought at first but I guess I am almost lazy. Seems like do it right the first time and I won't have to redo it later situation.

@Alan
Excellent idea except the shop is rather small as is now at 13+ X 18+ .,..Also the house is not that far although it is totally separate. It makes you be dang sure you don't need to go back in the house BEFORE you start a project.

So I just need to figure out the best way to plug both ends of the CI pipe after I figure out how to cut it. The sawzall might get to be used for this along with 3 - 4 blades.

The best way to plug the cut pipe ends is with a rubber cap with stainless steel clamp, Fernco is a brand name sold in the BORGS. For cutting the pipe I found the best blade to be "The Torch" metal cutting blade sold by Milwaukee. I recently cut quite a bit of CI sewer pipe and never had to change the original blade.

Since this is a vent pipe don't forget to cap the the end above the roof or eventually it will fill with rain water etc. which is not a good thing

merrill77 · 05-24-2009, 03:07 PM

You didn't mention your goals for dust collection. If it is strictly convenience and/or cleanliness, a short flex won't kill you...but may have a noticeable effect. But I'd cut and plug the pipe if you are sure you'll never use it.

If your goal for dust collection is health/safety, than you really need 6" ducts and keep the joints and flex to an absolute minimum. Most likely in this case, the pipe has to go.

MIKE NOAH · 05-24-2009, 03:57 PM

I am going to suggest you strongly consider 6" piping like the others have said, especially if you are close to the beginning of your run and close to the collector. With the interference problem pvc can be manipulated a little with a heat gun. That being said be sure you are wearing a mask and/or a fan for ventilation. The fumes are almost odorless but toxic.

McRabbet · 05-24-2009, 05:13 PM

If you use either 4" or 6" S&D (D2729) pipe, then consider making an offset using 4 22-1/2 degree els and short lengths of straight pipe to build an offet saddle over the CI pipe if you decide to leave it in place. If the CI descends at a corner, then I'd use a pair of 45 degree elbows and a straight section of pipe to build a sweep that goes in front of the CI pipe. The fittings should be available at Lowe's.

Dudelive · 05-24-2009, 07:59 PM

Originally Posted by Glennbear

The best way to plug the cut pipe ends is with a rubber cap with stainless steel clamp, Fernco is a brand name sold in the BORGS. For cutting the pipe I found the best blade to be "The Torch" metal cutting blade sold by Milwaukee. I recently cut quite a bit of CI sewer pipe and never had to change the original blade. Since this is a vent pipe don't forget to cap the the end above the roof or eventually it will fill with rain water etc. which is not a good thing

Many thanks for this information, to be honest I had my doubts as to it working like you said. So I went and bought The "Torch blades" and it was a breeze to cut. A darned lot easier than I had thought. The second cut was as easy to cut as the first.

Hats off to you for the excellent information that really does work.