Slip Hub?

[Chuck]

I was trying to figure out exactly what this term means, and the only references to it I could find pointed back to Valterra parts. Can't find a "plumbing" definition for the term.

"Slip", or "spigot", and "hub", yes. but not "slip-hub".


The reason I ask is that I'm wondering how dump valves connect to these standard aftermarket black/grey tanks. The vent fitting in the top of my old black tank was "female", and accepted the 1 1/2" vent line, but is thin walled, and secured by a band clamp. Are the 3" dump outlets the same sort, secured with a clamp? It would seem a bad idea to permanently glue a fitting there, in case things ever need to be removed/repaired.
Also, on poly tank information, it says that you can't glue stuff to them...

[Sneakinup]

I've changed from Thetford to Valterra. Here is a pic of the valve... with the "slip hub".

[Sneakinup]

Forgot to add that the slip hub is the black pieces on either side of the valve. The white pvc is glued in to fit in to my existing tank flange.

[Chuck]

In the first pic, the piece on the right looks just like the thetford flange that is on my original tank. (and again, I don't know how that is attached, and I thought you couldn't glue stuff to polyethylene).

So that "stub" of pvc pipe is glued to the valterra flange on one end, but how does it attach to the tank? glue? do you still use the Thetford flange?

[danlehosky]

Chuck, a slip or spigot end is generally referencing an end of a fitting or valve that is "pipe size". These are also called street fittings. In the old days of cast iron pipe that was leaded the ends were hub or spigot. the spigot end fit into the hub. They are used sometimes where space is limited. The flange I would imagine would be a gasket fit with the four screws tightened to form the gasket seal. Tighten them evenly and don't overtighten them. Remember that plastic pipe is solvent specific. You can't use ABS glue on PVC or vice versa. Hope this helps.

Dan

[snakecharmer]

I found a "Transition " cement at Home Depot that allows you to glue ABS to PVC

Also, I beleive you'd need to fabricate an adaptor plate to mate Valterra Valves to the original Thetford Valve mounting flanges which are attached to the black water tanks. Vintage Airstream.com has a "how to" on this under "Thetford Brass Valve Replacement." It's a little different than what you have, but the idea should work
Although I've never tried it, there is a product called West Systems Epoxy that is claimed to adhere to the polyethylene material that some fresh water and holding tanks are made of.

[wahoonc]

If the pipe is the same size you want a Flexible Connector. They also make them to hook two different sized pipes together.

Aaron

[danlehosky]

Snake, transition glue will work but is a poor substitute for specifically formulated solvents that bond to PVC or ABS. The flex, vibration and movement will make this application difficult. If you have to mix the two pipe types "Fernco" type mechanical fittings are a much better choice..

Polyethelene pipe is extremely chemically resistant and widely used in labortory piping for this very reason. If this epoxy works, it will be a first. Generally, mechanical or heat fusion processes are the only ways to make long lasting effective joints in this pipe. I'm not saying it can't be done but I'd have to see the product specs.

Dan

[Sneakinup]

It's really very simple. The white piece of pvc is what fits in to the tank opening. It is held in place to the tank with a strap clamp. Be sure to put brush on pipe dope or it will leak. I had to smooth out the inside of the tank opening, as it was rough and wouldn't make a good seal. After that, I filled the tank completely on my bench and left it over night. Not a drop leaked out.

See attached pics.

For the rest of the connections I bought flexible rubber pieces. I added yet another piece of short pvc on the outer end of the slip hub to attache the rubber fittings to. They are lighter in weight and easy to take apart in the event I ever have to.

Hope that helps.

[Chuck]

Ok, that's what I was looking for. pipe goes IN to the tank; band clamp.

so did you use this special abs to pvc glue to glue the pvc stub to the valterra body? I'm assuming that the valterra valves are abs...but only because they're black, like the abs pipe...and rv's seem to always use abs.

can't get the abs around here. Not code in houses, for some strange reason, so nobody stocks it, except rv stores, and those are far and few between. And as everyone knows, every plumbing job requires at least 3 trips back to the store for the correct fittings. That's going to suck via mail order.

I do wonder how the thetford flange is attached to my original tank, though. Not that it matters; I'm not re-using it. Just curious. It is on there "but good"...but there's no band clamp. can't imagine that they spin-welded it, as its different material.

[Sneakinup]

I can't remember what glue I used, but I bought it at Lowe's. There is a retired plumber working at my local Lowe's that has helped me out hundreds of times. I brought in the pieces and he told me what to use and they are now happily welded together.

My Thetford flange took forever to get out. I didn't want to crack the tank, so I carefully heated it up with a heat gun to soften the goop (technical term) and then slid it out slowly. After all, it had been in there for 35+ years.

I have seen some 60's tanks where the Thetford was screwed to a plate on the tank, but being that yours is a 73 it should (no guaranty) be like my 77.

[Chuck]

yeah, same flange/different tank. pics here: http://www.airforums.com/forums/f420...ml#post1162033

funny, because they say (even on Inca's site, the manufacturer of these tanks) not to use glue. (shrug). Could you see remnants of glue/sealant when you took yours out? I wonder if its just a super-tight friction fit? (seems unlikely).

[Sneakinup]

No glue. It looked and felt just like 35 year old Vulkem... and there was a lot of it on both the black and gray tanks. Dried and caked. I'm guessing it was what I used... pipe dope. I used a small hooked pick to clean all the excess, then the heat gun. It took a while, but it started to move.

[CA_Tallguy]

Just a note - valterra has both hub/slip and spigot flanges available. I think that I have that right... Came here trying to clarify the difference. So the spigot end I believe is the same size as 3 inch or whatever pipe. And I'm wondering if I can just use one of those to tie into my tanks instead of the white transition piece sneakinup shows.

I think that I too am going to switch to valterra. The wide availability seems like too great of a benefit to pass up. Hopefully I can get the hole in my belly pan all setup so that they would be fairly easy to swap if the need should arise. Leaky valve? $15 bucks and probably an hours work under the trailer to fix.

I've spent a number of hours simply trying to understand what thetford valves I'd need should I want to swap those. (Apparently they are not clearly marked with an identifying and differentiating number.). At this point I think it's going to be easier to just go to valterra and I will be able to fix or replace them anywhere at anytime. Might even be able to get replacements 24 hours at walmart!