How to connect 4" hose to 4" SDH35 (not schedule 20 PVC pipe) (renamed thread)-a Canadian drama :-))

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Forum topic by MiniMe posted 01-15-2020 05:02 AM 1440 views 0 times favorited 34 replies Add to Favorites Watch
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312 posts in 658 days

01-15-2020 05:02 AM

If you are interested in how I got here please keep reading
If you just want the freaking solution skip to this post

I am having a hard time connecting my hose (4” PVC) to the 4” PVC pipe that I have (SDH 35)

This is what I have

This guy over here is using this pipe:

I have exact the same coupling piece he is pushing in here

but mine does not fit in.

Apparently there is thinner wall pipe (solid sewer pipe or schedule 20) that could be used to connect my 4” hose but I I can’t find any of them anywhere here in Ontario. HD is put of stock for Solid sewer pipe)

Any idea what he is using or what I should use to make this work?

I am reading that
The outside diameter is the same as Schedule 40, so it is compatible with all Schedule 40 and Schedule 80 fittings. Used mainly in stormwater and drainage applications, SDR 35 is a medium-strength pipe that falls between Schedule 20 and Schedule 40 PVC pipe.

34 replies so far

View Walker's profile


192 posts in 1079 days

#1 posted 01-15-2020 06:56 AM

you could use a router to make the walls of the pvc pipe thinner. If you’re trying to make a permanent connection you could also use a heat gun to soften up the parts and persuade them to fit.

-- ~Walker

View PeteStaehling's profile


102 posts in 1726 days

#2 posted 01-15-2020 11:33 AM

Not sure what you have available there, but I used the schedule 20 stuff and yes, it is the same outside diameter thinner wall thickness.

PVC becomes pretty pliable if heated with a heat gun, but working it can be tricky. Keep the pipe turing and moving until the whole end is pliable. The good news is that expanding it is easier than shrinking it, so heating it and stretching it over the fitting may be doable. I have done similar tasks with pvc in other applications. If you don’t have a heat gun a propane torch may work, but it is easy to overheat spots with a torch.

Some trial and error may be needed to get the hang of it, but if you screw up an attempt just cut it off and try again.

View controlfreak's profile


409 posts in 208 days

#3 posted 01-15-2020 11:37 AM

+1 on the heat gun. That is how I customize my pipe to accommodate odd fittings.

View MiniMe's profile


312 posts in 658 days

#4 posted 01-15-2020 01:16 PM

Well I am curious what he is using because in the same video he uses the fittings to do this

and again the black couple goies just right in..(this is what he is saying but in the picture below I see space between the black coupling piece and the white coupling piece

the video is here if you are curious

View EarlS's profile


3427 posts in 2955 days

#5 posted 01-15-2020 01:19 PM

If you have a Home Depot – look outside in the garden center for drain pipe. It is usually by the corrugated, perforated black flex hose and such.

-- Earl "I'm a pessamist - generally that increases the chance that things will turn out better than expected"

View MiniMe's profile


312 posts in 658 days

#6 posted 01-15-2020 01:31 PM

If you have a Home Depot – look outside in the garden center for drain pipe. It is usually by the corrugated, perforated black flex hose and such.

- EarlS

this is all they have

I checked the corrugated section after reading around here -went there yesterday around 10PM (got in 10 min before closing) to see what a heck I am missing here…I could not find anything else
Funny thing is that I tried the black cupler which I had with me this time and it went in in one of the pipes from the same stack from which I picked mine initially. It went in a little bit forced but it went in eventually
Another thing that bothers me here is that you pay 16CAD for a 4”x10’ pipe an you pay 8CAD for the black coupling at Lee Valley

View MiniMe's profile


312 posts in 658 days

#7 posted 01-15-2020 01:38 PM

Mistery solved, the guy below is in Australia -I guess different pipe sizes than here in US/Canada

Now I am totally confused and lost
I this video the guy is cutting the black coupling piece IN THE MIDDLE and the cut end fits right in in his pipe while in my case I can’t even push in the other end

View JayT's profile


6358 posts in 2818 days

#8 posted 01-15-2020 01:55 PM

Only thing I’m really seeing is that your pipe is listed as 4”/100mm. 100mm is about 3.95in. If it’s actual inside diameter is 100mm, then that 1/20 of an inch could be why the fittings aren’t going in as easily. The US made 4” Charlotte pipe that is in your second pic will have a true 4” inside diameter. I’m not familiar enough with actual vs nominal sizing of pipe in Canada to know if that’s the case or not .

-- - In theory, there is no difference between theory and practice. In practice, there is.

View Axis39's profile


145 posts in 204 days

#9 posted 01-15-2020 01:59 PM

Can’t you just buy the schedule 40 couplers? Maybe return the couplers from Lee Valley?

-- John F. SoCal transplant, chewer uppper of good wood

View MiniMe's profile


312 posts in 658 days

#10 posted 01-15-2020 04:48 PM

Can t you just buy the schedule 40 couplers? Maybe return the couplers from Lee Valley?

- Axis39

then how do I attach my hose to them?
The only way that seems to work is to attach a 4”to3” reducer to the 4” pipe and then the hose fits perfectly but I am on 3” with a 3/4 HP Dust collector -I am trying to avoid that

View Fred Hargis's profile

Fred Hargis

5928 posts in 3100 days

#11 posted 01-15-2020 05:54 PM

When you pair plumbing pipe that is made to standards to something like DC hoses, etc. that aren’t made to any standards (as far as I know) nothing fits perfectly; sometimes not even closely. So you wind up making do with duct tape, heat guns, hacksaws, and other paraphernalia to get things together. With the plastic you can shrink/expand it with heat, or cut slits to squeeze it down, or make filler out of whatever is handy. All these connections might leak, so you’ll need to make them air tight. As for the wrong pipe…it goes back to this being plumbing stuff. You can’t use the wrong pipe….it’s a matter of getting by with what’s available. Most of the gizmos WW’ing vendors offer to get the 2 together assume (I think) you have the thinwall PVC…which is the schedule 20 stuff. I suppose that’s because it’s what most folks choose since it’s generally a little cheaper and easier to deal with (weight wise). If you’re searching for a perfect solution I don’t think you’ll find it, at least I never have.

-- Our village hasn't lost it's idiot, he was elected to congress.

View MiniMe's profile


312 posts in 658 days

#12 posted 01-15-2020 08:24 PM

I can’t find schedule 20 stuff
It was discontinued with SDR35 that sits in between Sch20 and sch40

View CaptainKlutz's profile (online now)


2245 posts in 2101 days

#13 posted 01-15-2020 09:41 PM

+1 Wood working DC fittings are very difficult to work with. There is no hard standard, and the dimensions are all different. Sometimes even between the same parts from same mfg, they won’t fit each other.

IME – Those flex couplers in the video being cutting in half > are worst for size differences. I have several that are two big to fit inside several plastic fittings in my collection. The are easily 0.050 larger than the smaller ones that look identical, and work as intended.

My advice, try buying a different brand of coupler, or go into local wood working store and check all couplers in bin for the small ones.

Best Luck.

-- I'm an engineer not a woodworker, but I can randomly find useful tools and furniture inside a pile of lumber!

View RobS888's profile


2635 posts in 2452 days

#14 posted 01-15-2020 10:05 PM

Rockler has sanitation connectors that I have used. I wrap 2 inch masking tape around connectors when they are too small and have even used unions from HD to connect stuff that won’t fit.

I have been able to slide flex hose onto pipes to do away with any connectors.

-- I always knew gun nuts where afraid of something, just never thought popcorn was on the list.

View Madmark2's profile


716 posts in 1195 days

#15 posted 01-15-2020 10:11 PM

The problem isn’t with th ID, it’s with the OD. The wall thicknesses of PVC (any schedule) varies from those of the black fittings. The OD of the black fittings varies from vendor to vendor. Buy all your fittings from the same vendor to reduce the risk of misfits.

The hose union middle only lucked out for that fit.

Buy flex couples to make these connections if you can (here in the US Home Depot has them in both 4” and 2-1/2”.

Barring that, cut a 1” deep X on the end of the large fitting. This will give you some dimensional tolerance when connecting. Use metal foil tape to seal the slits and a power driver to tighten the hose clamps enough to flex the fitting.

vacuum manifold before being metal taped – note slits end end of fitting

White PVC is great and all but clear piping let’s you find the clogs – and there will be clogs. Usually where the joints are.

Also, be sure to use metal blast gates as the plastic ones are sloppy and break. The plastic gates can’t stand the stresses of a flex hose while the metal ones can.


-- The hump with the stump and the pump!

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