text: Cast iron DWV pipe and fittings are still used in premium construction because they muffle the sound of wastewater rushing through them, but today they are rarely joined with traditional lead joints. Instead, pipe and fittings with plain (non-belled) connections are butted against each other, and clamped with special rubber sleeve (or "no-hub") fittings. The rubber sleeves are typically secured with stainless steel worm drive clamping bands, which compress the rubber to make a tight seal around the pipes and fittings. These pipe clamps are similar to hose clamps, but are heavier-duty and ideally are made completely of stainless steel (including the screw) to provide maximum service life. Optionally, the entire rubber sleeve may be jacketed with thin sheet metal, to provide extra stiffness, durability, and resistance to accidental penetration by a misplaced nail or screw. Although the fittings are not cheap, they are reasonably durable (the rubber is typically neoprene or flexible PVC). 
  An alternative design also allows the selective use of belled fittings made entirely of flexible rubber, including more-complex shapes such as wyes or tee-wyes. They are secured to cast iron pipe segments by use of stainless steel worm drive clamps. Because these fittings are not as stiff as traditional cast-iron fittings, the heavy pipe segments may need better anchoring and support to prevent unwanted movement. The lighter rubber fittings may not muffle sound as well as the heavy cast-iron fittings. 
  An advantage of flexible rubber fittings is that they can accommodate small misalignments and can be flexed slightly for installation in tight locations. A flexible fitting may be preferred to connect a shower or heavy tub to the drainage system without transmitting slight movements or stresses, which could eventually cause cracking. Flexible fittings may also be used to reduce the transmission of vibration into the DWV system.
  If necessary, clamped joints can be disassembled later, and the fittings and pipe may be reconfigured. However, it is often not customary to re-use the clamps and rubber sleeves, which their previous installation may deform and may not seal well after rearranging. Clamped fittings may occasionally need to be disassembled to provide access for "snaking" or "rodding-out" with a unique tool to clear blockage or clogs. This is also an indication that a clean-out fitting could be installed to provide easier future access.