Operation & Maintenance

1. What maintenance is required for the vacuum station equipment?

The vacuum vessel requires no maintenance other than external painting, and for this reason no standby vessel is required. The minimum of two vacuum pumps are each sized to be able individually to perform the duty required and in the event of one failing or being maintained, the other pump will operate the system. This also applies to the sewage discharge pumps.

In general then, the vacuum station requires no more maintenance than a conventional pumping station.

2. Are blockages encountered in vacuum sewers?

This is an extremely rare occurrence. The sewage is moved through the vacuum sewers at high velocities of up to 6 metres per second in the form of a foamed plug which makes the pipe work self-cleaning. In addition, the system’s vigorous action breaks up solids, meaning that the blockages are very rare.

3. Is the vacuum main prone to damage and if so what procedures are to be followed to locate the fault?

If the recommendation regarding the use of polythene pipe with electro-fusion fittings is followed, then the vacuum main is not prone to damage as this produces an extremely strong and resilient integrated line. The only way that this is likely to be damaged is by unlawful or careless excavation. In the event of this happening, the telemetry alarm will be raised and the maintenance operative will quickly be able to isolate which line has been damaged. It will be a simple matter then to locate the position of the excavation that has damaged the pipe. Location of any damage can be achieved by use of Redivac’s monitoring system, by use of the marker/tracer tape or by simply looking to see if any holes have been dug in the vacuum sewer trench line.

In the very unlikely event of a leak developing in a vacuum main from a cause other than excavation, then the method of locating the leak is as follows:

• Each main is shut down in turn at the station so that the main on which the fault lies is quickly ascertained.
• By shutting the isolating valves it can be established on which branch of the main the fault lies.
• Using the Redivac valve monitoring system and a portable monitor, it is possible to determine between which two valves the fault has occurred. In practice, this distance is unlikely to be much more than about fifty metres. The benefit of using the valve telemetry system in this diagnostic mode is that the number of isolation valves on the system can be kept to a minimum.
• Because the existence of a fault would be immediately brought to the attention of the maintenance authority via the telemetry, the fault could be quickly repaired and not remain undiscovered, leaking pollution into the surrounding soils as can happen with a conventional system.

As part of the training offered by Redivac to the client’s maintenance operatives, the above procedures are fully described and demonstrated in detail.