What would cause it to expand and contract over time? what is the coefficient of linear expansion of PVC over ABS glue


It isn't my place to tell you to leave it alone but if you did it would likely be still working fine many decades from now.

All the pieces leading from the overflow down to the sump will NOT be under pressure. You could just add a layer of silicone on the outside along of all the joints and it should be fine. No pressure = no problem.

The return lines from the pump up or anywhere there is pressure will need to be more secure.

Hopefully this will save you having to redo ALL the plumbing and only leave you with some to be fixed.

The return PVC lines for my skimmer are a combination of threaded fittings and press fit with a little teflon tape, no solvent or glue whatsoever. Been that way for two years, no problem. The 'pressure' of the flow is so low through those lines, it's unlikely to ever leak unless I mess with it. A little salt creep is all I've had and I simply wipe that up from time to time. Not sure I'd do that with a lengthy drain or return, but I've found that new PVC and ABS material fits together very snugly if you push and twist enough. The only concern would be vibration from a return pump or something similar, which may shake things loose over time, but you've glued yours and even with the 'improper' solvent, you'll likely be ok. The silicone recommendation around the outside sounds like a good idea rather than starting from scratch.

With all this response I decided last night to take a pair of huge pipe pliers and a hammer to a spare piece (pipe & ball valve) that I had cemented together with the ABS glue. It did not give way easily, the pipe was pretty much mangled before the glue let go. That being said though when it did fail the piece came out of the joint like the glue didn't exist. The inside of the ball value looks like new, it seems the only place the glue attached to was on the very end of the pipe. It kind of reminds me of the behaviour of some glues on metal or glass, once you unseat it a little it just completely releases.

In the end I could easily see the glue releasing if it was expanding and contracting a lot but as mentioned in the posts I'm not sure if that would even occur if you're running a constant temperature through the pipes. As suggested I'm thinking for the drains I’m just going to leave them the way it is. The return I may redo as it runs along the outside of the tank but I will put that off till I have to move the tank again once the floors have been replaced.

Maybe the Rona or Home Depot guys will give me deal, they pretty much know me by name now... :biggrin:

With all due respect to what others have said about leaving it as is, at the end of the day it's your floors that are at stake, not theirs.

wrong glue
 

I personally would not be too concerned. As someone else has said the operating pressure is very low. I have a setup with a mag 12 return on 3/4 inch pipe. I wrap the pipe ends with teflon tape and press them together. I don't use glue in case I want to make changes. I have used this type of plumbing on my pond outside for years with no problems. My tank has been up and running for almost a year. My setup is in the basement and there is a floor drain under the tank. I would use glue if I was in rental or condo unit and did not have the drain in the floor. Clarence

I'll tell you two things.
1) There is very little chance you will have a problem with the joints. It takes years and years before the bonds will break and more than likely you will have moved on to another tank or different plumbing.
2) I would still redo the plumbing just for peace of mind. As long as your tank is set up you will always have the fear that the plumbing is going to fail. The time and money spent to redo the plumbing is well worth that peace of mind.

I'd redo. Always have it hanging over you when/if it's going to leak plus if you're married, explaining to the other half, ya I knew it was wrong but thought it would be okay, not worth it.