Deep sump Deluxe bottom drain with Air Diffuser fits 4" pressure pipe (115 mm o.d), large dome supported by removable centre stem for easier maintenance,
 

Concrete version pictured suitable for fibreglassed and painted ponds

Also available for liners with separate plastic ring and stainless screws, 

Both versions have a separate 1" pressure socket for the air supply, which can be used for a conduit to attach the 10 mm hose required to supply air to the diffuser (hose not supplied available in our separate listings).

An optional bung kit is available for the air supply from inside the drain to the central stem, a small piece of 10 mm hose and 2 clips are also required but not supplied with the air bung option. The bung option does not require the long hose to be threaded down the 1" pipe.