Twin-Pump Maintenance
The high-output models run two pump barrels in sequence. What that means for wear, why the two sides are serviced as a pair, and the one check owners can do themselves.
Two barrels, one delivery
The twin-pump models deliver roughly twice the airflow of the single-pump machines at the same pressure, which is what makes the deeper ratings possible — the S9 and S77 move 95 and 160 litres a minute against the S6's 63. The second barrel is a staging stage rather than a spare: air from the first feeds the second, so the two are matched and always serviced together.
Why they are a matched pair
If one barrel is replaced and the other is left at half its life, the mismatch shows up as a delivery that sags as you descend — that is the second stage asking for more than the worn barrel can hold, and it feels like a regulator fault rather than a pump fault. Pairing the work avoids a return visit that looks like something else entirely.
The owner check that matters
Once a month, run the machine for two minutes with the second stage held clear and listen. Twin-pump machines should sound like one continuous note. A beat frequency — a slow wah-wah as the two barrels drift in and out of phase — is the earliest sign that one side is losing efficiency, and it is audible long before it shows up as reduced airflow in the water.
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