Internal Coupler for 4" & 6" Corrugated Drain Pipe Catalog Drainage Internal Coupler for 4" & 6" Corrugated Drain Pipe Description ADS ARC18 Leachfield / PVC Sewer & Drain / Schedule 40 / Platon Waterproofing Membrane / Form-a-Drain Foundation Footing System Internal Coupler 6353213 - 4" Coupler6COUP - 6" CouplerView Form-A-Drain Contractor Handbook Rates Please contact us for current pricing and availability. Request Availability