Northbound boats must maintain power and momentum in order to push through, due to the shallow, narrow nature of the canal in the tunnel (such that water has little space to pass around the displacement of the boat), and the relatively fast 2 miles per hour (3.2 km/h) southbound current of the canal.

The promoters asked William Jessop to assess their plans, and he produced plans for a rather different route, running from the Chester Canal basin through Wrexham, Bersham, Ruabon, Pontcysyllte, Chirk, Frankton and Weston to reach Shrewsbury.

[2] Rival parties supporting the different routes joined forces in February 1793, and the canal was authorised by Act of Parliament on 30 April of that year.

A whole series of alterations and deviations had been rushed through in the intervening months, and the canal at Chirk now crossed the River Ceiriog at a different location, resulting in a shorter tunnel.

The 8 miles (13 km) of canal eastwards to Frankton was opened immediately, because of the valuable trade in limestone from the Fron Quarries.