Water Floating with 192-Fiber – 7700 Meters (25,250 ft) in One Go

Told by fiber technician Michael Walther – a story from the field

Preparation is Key

We were assigned to install a fiber optic backbone cable between two small towns in central Sweden. A week earlier, we had already received the map data and scouted the area. When working with long distances, proper positioning is crucial – especially considering elevation changes and bends in the duct route.

The client asked if we should split the cable onto two drums since the total distance was 8 km (4.97 miles). But I declined – I know what my equipment and I are capable of. And skipping the splice means real cost savings for the client.

Equipment and Setup

We were installing into a 40/32 mm duct, using a 192-fiber cable with a diameter of around 8 mm (0.32 inches). Two cabinets along the route were looped together, just in case we needed to adjust the setup mid-installation. For water supply and pressure regulation, we used a flushing truck with 8 cubic meters (2,113 gallons) of water.

The Installation – Fine Control in the Field

We started with low pressure at 4 bar (58 psi) and let the water flow for about 5 minutes before feeding the cable. This helps prevent the cable from outrunning the water, a common issue at lower pressures. Initial speed was around 120–130 meters per minute (394–427 ft/min). After about 1600 meters (5,249 ft), the cable had gone past the water flow. We paused for a minute, then continued – now at 12 bar (174 psi) and 65 meters per minute (213 ft/min). As the pressure equalized, we dropped it to 8 bar (116 psi), which increased the speed to 108 meters per minute (354 ft/min).

Around 3000 meters (9,843 ft), we encountered what we call “spaghetti fiber” – the cable compresses and fluctuates in speed. You can hear it in the machine. But the Jetting V2 gives excellent feedback – it’s compact and responsive, yet powerful enough to handle these drums. By lowering the speed and increasing water pressure, we stabilized the flow again.

The Final Stretch – and a Sudden Stop

At 6000 meters (19,685 ft), we held a steady 65 m/min (213 ft/min) and 15 bar (218 psi) pressure – until the water ran out. We disconnected the hose and sent the driver to refill. Restarting can be tricky when that much cable is already in the duct, but after 15 minutes, we regained the right pressure and continued the job.

Result: 7700 meters (25,250 ft) installed in one go – no splice needed. We finished off by looping in the cabinets, slitting the ducts, and labeling the cable. Calling the client to say he could skip the expensive straight splice? Extra satisfying. 🙂

Advantages of Water Floating

Up to 50% longer installation distances compared to air
Water is a more efficient cable carrier than air
Acts as a continuous lubricant during installation

Downsides of Water

Higher cost due to the flushing truck
Slightly slower feed rate than air
If the network owner requires flushing the water out afterward, the cost increases further

My Recommendation from the Field

Use air for installations up to 3000–4000 meters (9,843–13,123 ft). Above that, water is the way to go. Of course, it depends on cable and duct type – but that’s my general rule.