Solvent weld mineral encrusted PVC pipe


  #1  
Old 07-13-15, 01:31 PM
P
Member
Thread Starter
Join Date: Oct 2009
Location: Nevada
Posts: 65
Upvotes: 0
Received 3 Upvotes on 2 Posts
Solvent weld mineral encrusted PVC pipe

I have a need to solvent weld a fitting onto a piece of PVC that is encrusted with mineral deposits (calcium deposits from a dripping connection).

I assume that I need to remove all the calcium deposits from the area to be solvent welded, as the deposits will prevent the primer/cement from making contact with bare PVC and softening it. I can scrape most of the deposits off with a paint scraper, but to get all of it off I think I'm going to need to either sand to bare PVC, or use a chemical to get rid of the remaining deposits.

Is there any danger of sanding too much PVC off and preventing a good bond, if I use something like 320 grit sandpaper to get to bare plastic? Should I try using something like CLR or Lime Away to chemically remove all traces of minerals instead, so the fit of the pipe into the fitting remains tight?

BTW, this is on a piece of ordinary 3/4" Schedule 40 PVC. If I want to get to a pristine section of PVC I would need to dig up a lot of soil (this pipe is going to feed a manifold of four drip valves for garden irrigation).
 
  #2  
Old 07-14-15, 06:05 AM
P
Group Moderator
Join Date: Mar 2003
Location: NC, USA
Posts: 27,592
Received 2,144 Upvotes on 1,920 Posts
Yes, there is a danger to sanding too much especially if the mineral deposits are spotty. Some PVC drain piping is cellular core meaning there is solid PVC in a thin layer on the surface and the interior is more like foam. Most 3/4" is not so you should be OK in that respect.

Generally easiest is to just cut out the encrusted pipe and replace with new. You don't have to replace the entire pipe. Just cut it back until you get good, clean pipe and use a coupling and glue on a nibblet of new pipe.



You can dissolve away the minerals but generally stuff like CLR, Lime Away and white vineagar will really test your patience. Muriatic (hydrochloric) acid when used properly can do the job much faster... but read up on using it safely. It's the strongest acid the average person can go buy so you have to handle it properly as from the can it is strong enough to burn skin, lungs and eyes.
 
  #3  
Old 07-14-15, 11:39 AM
P
Member
Thread Starter
Join Date: Oct 2009
Location: Nevada
Posts: 65
Upvotes: 0
Received 3 Upvotes on 2 Posts
Thanks for the reply. I pretty much came to the same conclusion after a little more searching and reading about bonding problems when there was a loose fit between pipes.

I'm familiar with muriatic acid and its dangers as we have a pool at our vacation house, and the fill water has high alkalinity.

I may try to rig something (rubber bands and plastic bags) so I can get a long contact time between the CLR and deposits, to try to remove them, but if that doesn't work I'll dig until I find some clean PVC and glue to that. Thanks again for the advice.
 
 

Thread Tools
Search this Thread
 
Ask a Question
Question Title:
Description:
Your question will be posted in: