PVC to Cast Iron Toilet drain... which Fernco?


Old 03-12-17, 11:29 AM
Thread Starter
Join Date: Apr 2008
Posts: 32
Received 0 Votes on 0 Posts
PVC to Cast Iron Toilet drain... which Fernco?

I had a broken toilet flange. I cut off the old lead drain pipe, leaving a 1.5" stub before the cast iron fitting. How should I connect the new PVC pipe? I tried to link pics of the possible solutions.
  1. Use a shielded 4" Fernco coupling to a PVC 4" to 3" reducer, then 3" PVC pipe. Pic#2
  2. Pass 3" PVC through a Fernco 3" to 4" reducing coupling, with PVC extending deeper into the Cast Iron. Pic#3
  3. Your incredible solution

Name:  20170312_135034.jpg
Views: 3947
Size:  25.5 KBName:  20170312_135232.jpg
Views: 7649
Size:  23.3 KBName:  20170312_135144.jpg
Views: 9943
Size:  23.1 KB
Sponsored Links
Old 03-12-17, 11:55 AM
chandler's Avatar
Banned. Rule And/Or Policy Violation
Join Date: Dec 2005
Location: USA
Posts: 39,967
Received 6 Votes on 6 Posts
3) 4" shielded Fernco to 4" PVC to 4" elbow to 4" flange.
Old 03-12-17, 06:01 PM
Thread Starter
Join Date: Apr 2008
Posts: 32
Received 0 Votes on 0 Posts
Based on the 4" pipe to street elbow to flange being too high, I plan to reduce the pipe size to 3"... see below. I've also been told that 3" is better because it flushes at a higher velocity.

The distance from the top of the stub to the top of the rafter is 1.75". The rise for the 4" PVC Street elbow is 3.25". 3.25 - 1.75 = 1.5" above the rafter.

I planned to use 0.75" plywood + 0.5" backboard = 1.25"

That leaves me with a street elbow 0.25" above the backboard before I attach the flange. As I understand it, the flange should sit flush with the backboard, not above it. Am I wrong - should the flange sit atop the level of the floor tile? How would I screw down the flange if it is sitting on the tile?
Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is On
Trackbacks are Off
Pingbacks are Off
Refbacks are Off

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