PVC Connection Question

I live in Beijing and I am trying to connect a 25 mm outside diameter PVC pipe to a 1 inch connector. There's about a 2 mm difference in diameter. I am trying to connect a pvc pipe coming from an over the ceiling AC unit to a connection to an under the sink drain pipe. I could not find the correct fittings in China and that's why I am mixing a metric sized pipe to a American sized fitting. The connection is not under pressure since it is a condensation run off from the AC to the drain.

Steve McIntosh
Beijing China

Interesting problem. I don't think it will work for this reason. PVC is joined by solvent welding, not actual glue. The chemical in the so-called glue melts the surfaces of the pipe and fitting briefly. When they are joined together, the two surfaces flow together and then solidify. It's very similar to welding metal, except with metal you can use a filler to make up for a little gap between the two pieces. With PVC, there is no filler, the "glue" is just a solvent. This means the pipe and the fitting need to fit with very close tolerances. If you can't find the fittings you need in China, you might be able to have a friend or relative in the US send some to you. I don't know what kind of mail service you have, but UPS advertises about their overnight service to China.

Whoops! I turned things around. You have the US sized fittings but metric pipe. Don't have a clue what you can do about that. Seems strange that if you could buy the metric pipe they don't have fitting for their pipe!

Silicone?

Can I just use silicon to fill the 2mm gap between the two pvc connectors?

China does not have a lot of the plumbing materials available in the West that's why I am using two different types of connectors and they use a lot of silicone to make connections.

You can try the silicone, I can say it will work or not. I would advise you to support the pipes well to avoid any strain on the joints as I fear they could part. Monitor the joints when there is water draining to make sure you have no leaks. Another possibility to make the connections is with Fernco style couplers. They may or may not be available either, but even hoses clamped to the pipe ends would probably work.

You can heat up PVC pipe and expand it to match the fitting. Use a heat gun and have a wooden dowel made to the right size to insert into and expand the pipe. Then use the solvent cement to cement the pipe into the fitting.

Yes, and maybe you can find an expandable plug to use inside the pipe rather than having to make a dowel.