Another PVC Pipe Question

[MoonRiver]

I'm giving up on trying to use x's and t's with 3/4" pvc pipe to make a greenhouse. There is just too much stress on the connections and the pipe keeps breaking loose. The pvc seems to be so degraded by the use of cleaner that I can't reglue a piece that breaks loose. Even when I really slobber the glue on, there is just too much play to get a tight fit.

Here's my question.

Does 1/2" pipe fit inside of 3/4" pipe? If yes, is it a tight fit?

Does 3/4" pipe fit inside 1" pipe? If yes, is it a tight fit?

I need 18" lengths. What I'm thinking of doing is cutting 2 pieces at 8' each and then a smaller diameter piece to connect the 2 pieces. Run it about 6" inside each end.

Thoughts?

[Darren]

There are a couple of companies that sell benders to make greenhouse hoops out of conduit. Those will last longer than run of the mill PVC. If you really want to use PVC, buy the so-called furniture grade stuff. It lasts longer and it has a much tighter fit with the fittings. I had to actual sand PVC pipe to get it to fit.

[Windy in Kansas]

I think that I would be questioning the quality of your PVC pipe and fittings. A properly glued fitting does not fail without actually breaking. The glue melts or welds the PVC together and it becomes as one.

I'll put it this way about the pipe, fittings, and glue---something sure isn't right about the combination or quality or both.

Have you viewed the material at http://www.hightunnels.org ?

With wind and snow loading even in your area I can't imagine getting by with less that 1¼" or 1½" PVC instead of just ¾".

Even with them giving some shading I wonder if 2X3s or 2X4s wouldn't work better? They are pretty inexpensive in the stores these days.

[Bearfootfarm]

A properly glued fitting does not fail without actually breaking

They aren't designed to be put under the stress of bending.

The simplest way to hold them together is drill and bolt the connections

[Windy in Kansas]

Originally Posted by Bearfootfarm

They aren't designed to be put under the stress of bending.

I do understand that, but the point is that the glue joint is failing, not the fitting itself. I contend that the fitting itself will fail before a properly glued joint will as it is melted/welded together via the cleaner and glue.

[beowoulf90]

Originally Posted by Windy in Kansas

I do understand that, but the point is that the glue joint is failing, not the fitting itself. I contend that the fitting itself will fail before a properly glued joint will as it is melted/welded together via the cleaner and glue.

If the joint is failing then you are either using the wrong glue or the batch you have is bad..

PVC joints don't fail unless the pipe or fitting breaks.. Proper joints are more like welding to pieces of plastics together, they become a single piece..

Also make sure you have pipe and fittings that are the same..

If you are using a schedule 40 pvc pipe, use a schedule 40 fitting..

[MoonRiver]

Originally Posted by Windy in Kansas

I do understand that, but the point is that the glue joint is failing, not the fitting itself. I contend that the fitting itself will fail before a properly glued joint will as it is melted/welded together via the cleaner and glue.

It doesn't pull straight out. What happens is that at the very peak where the pressure is greatest, it pulls so hard I think it stretches the hole larger until the pipe pops out sideways.

I did go buy some 1/2 pipe to see if I could use it as my bridge piece. It fits inside the 3/4" pipe, but is too loose to glue.

I think I will try screws next.

Part of the problem may be that my base is only about 8'6" (width of the slab). Most plans I have seen are for at least a 10" width, so I might be generating to much pressure for the PVC.

At this point, I am having fun just trying things. PVC is pretty cheap so mistakes are not costing me much.

[OkieDavid]

Originally Posted by MoonRiver

At this point, I am having fun just trying things. PVC is pretty cheap so mistakes are not costing me much.

That's the spirit. Also, from your description of the pipe pulling out from the joint it sounds like either you have an old/bad can of glue or you aren't giving it sufficient time to set up. I'd try a new can of glue, remember to twist slightly when pushing the joint together and give it 30min or so to set up before putting pressure on the glue joint.

[Windy in Kansas]

I like your spirit too with trying to find a solution.

Guess I should go to the hardware store and buy a piece of pipe and some fittings and some glue to see if I can get anywhere near the same failure you are. Sounds to me like you have bad products.

[MoonRiver]

Originally Posted by OkieDavid

That's the spirit. Also, from your description of the pipe pulling out from the joint it sounds like either you have an old/bad can of glue or you aren't giving it sufficient time to set up. I'd try a new can of glue, remember to twist slightly when pushing the joint together and give it 30min or so to set up before putting pressure on the glue joint.

I've used 2 different cans of glue and drying time has been as short as 15 minutes and as long as 24 hours. Right now, I have 6 out of 8 x connectors that are holding. Have no idea which can of glue was used on which connector. I tried making 2 today with new PVC pipe and new t-connectors. Real careful to clean and glue them. Made sure pipe was pushed all the way into connector and twisted. Laid flat for about 30 minutes to cure. Both failed immediately when I bent them.

I think I will pick up a few 45 degree elbows tomorrow. Have a straight 4' pipe to 45 degree elbow on each side. Then 5' to t-connector to 5' pipe to elbow. This will give me a little more head room on the sides and less stress on the t-connector.

[Txrider]

Originally Posted by MoonRiver

I've used 2 different cans of glue and drying time has been as short as 15 minutes and as long as 24 hours. Right now, I have 6 out of 8 x connectors that are holding. Have no idea which can of glue was used on which connector. I tried making 2 today with new PVC pipe and new t-connectors. Real careful to clean and glue them. Made sure pipe was pushed all the way into connector and twisted. Laid flat for about 30 minutes to cure. Both failed immediately when I bent them.

You probably need to give it longer before you stress it.

I have glued literally tens of thousands if not hundreds of thousands of PVC fittings..

You need to use the right PVC cleaner and glue for the pipe you have.

You also need to make sure you use the cleaner thoroughly on both the pipe, as well as the inside of the fitting, and liberally put glue on both the pipe and on the inside of the fitting, and give it a slight twist when you put it in.

Also make sure to hold the pipe tightly all the way into the fitting for a minute or two, because it -will- shove itself partially back out of the fitting many times if you don't hold it all the way in until it sticks well.

What folks are saying is correct, it should be bonded into one peice when cured and not be able to come out unless the pipe itself breaks. The cleaner and glue don't really glue the pipe, they melt it and fuse it into one piece when done correctly.

But.. Even though you can glue it and even run water under pressure through it in a few minutes, it takes longer then that to really cure and form a permanent fused bond. I have pulled apart well glued joints after 10 minutes if not a bit more, if you put enough pressure on the joint twisting or turning before it is cured it will come apart, as it is still melted a bit in the actual joint and softer then the pipe and will give way before the pipe actually breaks.

I would try putting the joints together right and giving the joints 24 hours even or more to cure before putting that kind of pressure on the joint and try it that way and see what happens. Much more time in very cold weather as that multiplies curing time. I think you'll find it'll work better.

[jwal10]

Use this AND their purple primer....James

http://shop.tjb-inc.com/cristys-red-...use-p1250.aspx

http://www.tchristy.com/SpecSheets/PurplePrimer.pdf

[PD-Riverman]

Get you some number 6 screws about 1/2" and around a 1/8th drill bit, With your pipe laying flat-----drill each joint 3 times making sure not to drill on the top(looking at a clock dial and the top where the plastic will touch is 12 oclock---drill at 10, 2 and 6 oclock position). Make sure all your fittings are glued as good as can be before you drill. Then drill and put these screws in----Problem should be solved. Good Luck!!

Originally Posted by MoonRiver

I've used 2 different cans of glue and drying time has been as short as 15 minutes and as long as 24 hours. Right now, I have 6 out of 8 x connectors that are holding. Have no idea which can of glue was used on which connector. I tried making 2 today with new PVC pipe and new t-connectors. Real careful to clean and glue them. Made sure pipe was pushed all the way into connector and twisted. Laid flat for about 30 minutes to cure. Both failed immediately when I bent them.

I think I will pick up a few 45 degree elbows tomorrow. Have a straight 4' pipe to 45 degree elbow on each side. Then 5' to t-connector to 5' pipe to elbow. This will give me a little more head room on the sides and less stress on the t-connector.

[Cheribelle]

Self drilling screws cost a bit more but save a step and some hassle.

[cowboy joe]

I've made greenhouses out of PVC before but have always used 1" or larger pipe. I never glue the joints either. The pressure from the covering keeps the joints in place and allows the pipe to flex in the fitting during windstorms or periods of heavy snow load seems to prevent breakage. I have had some fittings break but not until 3 or 4 years after the structure was built. Most of these failures appear to be due to degradation from the sun's UV rays.

[foxtrapper]

Originally Posted by MoonRiver

Even when I really slobber the glue on, there is just too much play to get a tight fit.

---and---

What happens is that at the very peak where the pressure is greatest, it pulls so hard I think it stretches the hole larger until the pipe pops out sideways.

Sounds very much like you are using fittings that are too large for the pipe. The right size slips together snugly and smoothly. You never need to "slobber glue on" for a tight fit. The glue is not the fit filler.

[CarolT]

Another question, are you doing all this outside and what temperatures are you working with? Think cold can prevent glue from working correctly?

[Usingmyrights]

If you use the gray PVC you can use a hairdryer/heatgun to bend it to help take some of the stree off of it. These also come with a bell end built in which should further help. With enough heat you can make it as flexiable as a cooked noodle. Thats what electrians do to do their underground pipe runs. They've got a hotbox too, but its not necessary