PondMAX 4″(100mm) Heavy Duty Bottom Drain with Air Diffuser

If your pond is deeper than 60cm, a bottom drain is optional — it's the single most effective way to stop fish waste, uneaten food and organic sludge from building up where your fish spend most of their time. The PondMAX 4" Heavy Duty Bottom Drain sits at the lowest point of your pond, continuously pulling debris off the floor and into your filtration system before it has a chance to break down and foul the water.

Built from tough, roto-molded material for long-term strength under the liner, this drain features a welded threaded inlet, a threaded centre stand pipe that locks the dome lid securely to the base, and sixteen stainless steel screws for a durable, leak-resistant assembly. The large dome lid keeps fish and larger debris out of the pipework while still allowing fine waste to be drawn through.

What sets this model apart is the built-in air diffuser in the dome lid. Air is delivered up through the centre stand pipe via a 1/2" tubing adaptor (recommended air flow 0.5–1.5 CFM), gently agitating the pond floor around the drain. This keeps waste in suspension so it's carried away rather than settling and compacting — particularly useful in koi ponds where fish stir up the bottom and waste volumes are higher.

Designed for a 4" female connection with a 4" male/slip adaptor included, this drain suits new pond builds and koi pond retrofits alike, and pairs naturally with a skimmer box and external pump or filtration system for a complete bottom-to-surface cleaning setup.

Key Features

• Heavy-duty roto-molded construction for durability under the liner
• Built-in air diffuser lifts waste off the pond floor for better filtration
• Welded threaded inlet — no rubber coupling required
• Threaded centre stand pipe securely locks dome lid to base
• 16 stainless steel screws for a secure, long-lasting assembly
• Large dome lid protects fish and blocks large debris
• 4" female connection, 4" male/slip adaptor included
• Ideal for koi ponds and any pond over 60cm deep

Specifications

Who this suits

Best suited to koi ponds and deeper ornamental ponds (60cm+) where waste settles on the floor faster than surface skimming alone can remove it. Commonly installed at pond construction stage, but can be retrofitted into an existing pond with liner modification.

Need help sizing your pond plumbing? Call 1300 238 288 — our team can talk you through drain placement, pipe sizing and pump matching for your setup.