How do I connect a 12 inch culvert to an 18 inch culvert to prevent erosion around the joint?
Question:I have slipped the end of the 12 inch culvert into the 18 inch culvert but need to seal the joint where they connect so that the backfill around the pipes won't erode and clog the larger 18 inch culvert. I am thinking about concrete. Any suggestions?
Answers:
Another way is to use a spray foam like great stuff, put small blocks around to hold the 12" centered in the 18 and start filling the gap with the foam. It is used here in Blackfoot Id for irrigation pipes to seal the corrugated pipe. I used it on a 32" to 24"and it was under my driveway and have had no problems with it & is reeeeeeaaaaallll easy to do.
Get a culvert adapter reducer (18 to 12" ) and install it.
You could make a cut in the larger pipe about 18" long and beat it down to the smaller size. Then fasten it with sheet metal screws. Your concrete idea is easier and would probably be my choice.
Possilby a large "fernco" type of fitting... but the concrete idea sets well.
I agree with using an adapter reducing the 18" to a 12" thus iliminating any leakage problems that can occur by using a filler to compensate for the difference in size.
all the suggestions so far are acceptable although I agree with you a well placed concrete band around the joint would suffice BUT are you connecting the smaller diameter culvert on the upstream side? if you place the smaller diameter downstream you will create a restriction point and may cause a stoppage at that point due to larger debris than the smaller pipe will accept.
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