How Silver Eel Passage works – VDV tech Eel Passages

VDV tech Eel Passages is a passive, gravity‑powered HDPE siphon that safely moves downstream‑migrating silver eels over dams, weirs, and pumping stations. No electricity. No moving parts. No fish handling.

• Patent Pending since 01 June 2026 – our unique design is protected. Unauthorised copying or commercial use will be enforced to the fullest extent of the law.
   
• Rust‑free construction – all metal hardware (bolts, nuts, brackets, valve stems) is marine‑grade 316 stainless steel. No rust, even in salt or brackish water.

Step 1 – large intake ring on the riverbed

A 4.6 m diameter HDPE ring sits on the riverbed. The ring has 60 intake holes on its underside, facing down. Eels swim underneath and enter through the holes – exactly where they naturally swim. Debris (leaves, sticks) cannot enter because the holes point downward.

Coverage: 21 m² of riverbed – eels do not have to search. They find it.
 

Step 2 – Gentle attraction flow (natural, No pump)

The ring is connected to a 30 cm HDPE siphon tube that runs up and over the dam. The natural flow of water through the siphon creates a gentle current inside the ring. Eels sense this current and are drawn toward the intake holes.

No electric pumps, no bleed pipes, no extra parts.
 

Step 3 – Gravity siphon lift eels over the dam

The siphon tube is placed over the dam crest. Both ends are submerged – one end in the upstream pool (connected to the ring), the other end in the downstream pool. Water flows continuously from the higher upstream side to the lower downstream side.

No pump, no electricity – just gravity.
 

Step 4 – Safe release downstream

Eels that enter the ring are carried gently with the water through the tube and released below the dam. No turbines, no spillways, no handling. They continue their migration to the sea unharmed.
 

Why VDV tech Eel Passage is different from conventional eel bypasses

Conventional systems typically have:

• Small intake box (1‑2 m² coverage)
• Only 4‑8 entry holes
• Holes on top or side (clog easily)
• Often need electricity or pumps
• Permanent, expensive construction

VDV tech Eel Passages offers:

• Large 4 m diameter ring (21 m² coverage)
• 60 eel entry holes
• Holes on underside – no clogging
• No electricity, no pumps
• Portable or permanent options
• Surprisingly affordable

Key benefits for silver eels

• Bottom entry – eels swim near the riverbed, exactly where the intake holes are placed.
• Large coverage – 4 m diameter ring covers 13 m² (or 4.6 m / 21 m².  Eels do not have to aim for a small opening.
• Debris‑proof – all holes face down. 
• Ring sits on adjustable legs (5–15 cm) above the riverbed. Leaves and sticks pass underneath – they cannot enter.
• Gentle flow – siphon velocity is low (<1 m/s). Eels drift, they do not fight.
• No handling – eels move voluntarily, no trapping, no transport.

What makes VDV tech Eel Pasages unique

• The 4 m diameter - 21 m² ring with 60 bottom‑entry holes
• Underside‑only intake (debris cannot enter)
• Large coverage combined with a simple gravity siphon
• Adjustable legs (5–15 cm) – adapts to any riverbed, prevents clogging

These features together are not available in any other eel bypass system.

Ready to see VDV tech Eel Passages in action?

We offer site assessments, rental contracts, and full purchase options.

Contact us for a demonstration or a quote.