# PVC Unions



## CamH (Jan 5, 2014)

So I was gluing a union today and I thought I had cut the pvc pipe about 1/4" to long so I shave some off. The dry fit was perfect. After I primed and and applied the glue, the PVC pipe slid in almost 1/4" more than it did during the dry fit! Guess the glue acted as a lubricant (there's irony). So now I have between 1/8" and 1/4" gap between the union connections. Does anyone think this will be a problem? Won't have time for a wet test for awhile to check.


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## PaulF757 (Dec 9, 2013)

If the o ring doesn't compress then it will leak. You can try plumbers tape, not the white kind but the pink, it's for larger thread count. If that fails then grab a coupling and extend it to what you need.


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## wtac (Mar 17, 2006)

If you've come up short, trying to screw it in tight will put stress on the other joints and you especially don't want that if it's plumbed to a bulkhead on the aquarium. 

Cut somewhere along the straight run and secure the union fitting. At the pipe gap, use a coupler and mark with a pencil so that each end of the pipe will be seated equally on each end of the coupler. Glue and insert the pipe into the coupler to the marked line.

When I plumb a system, I have it all mapped out well before hand. On a run, I measure how much I need from one fitting to another and add the depth of the socket of the fittings. 

If you choose to dry fit, take the time and chamfer the outer cut edge with a chamfer tool, file or 120 grit sandpaper of the pipe for two reasons:

1. there will be a raised edge making the diameter slightly larger and will not seat down all the way into the fitting

2. removing the sharp edge will prevent the pipe from planing/scraping the inner socket of the fitting. This scrapes away the solvent making a weaker joint and the curled up PVC shaving in the line will add to flow resistance. Also, the pipe will not snag and only seat part way into the fitting.

Also when you dry fit, mark the pipe where the fitting should be as the pipe will not always seat all the way into the fitting.

HTH


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## CamH (Jan 5, 2014)

Thanks guys! I'll fix it this weekend with your advice


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