Sewer and Equipment
1. What pipe materials and pressure ratings are required for a vacuum main?
The materials from which the vacuum mains can be constructed may vary depending upon what is most economical in a particular country. In reality any material that can be jointed to maintain a vacuum and can withstand a wheel loading when buried with an internally applied vacuum of up one Bar would be acceptable. However, in practice the preferred material is undoubtedly high density polyethylene (HDPE) with the jointing method being electro-fusion. The wall thickness specified by Redivac for HDPE pipe used in the UK would be SDR 17.6. For more details regarding Redivac’s recommendations for pipe thickness and strength in other countries please refer to Redivac’s specification for your area or contact your Redivac Agent or Distributor.
2. What is the maximum length of a vacuum sewer main?
Vacuum main lengths of 2500 to 3000 metres are not uncommon and are dependant upon the topography of the area to be served. The limiting factor when designing a vacuum sewer is not the distance from the collection station to the furthest valve chamber but the maximum static lift from the lowest interface valve chamber position back to the collection station.
3. What equipment is in the vacuum station?
The equipment in the vacuum station will typically consist of a collection vessel of either mild steel or glass fibre construction, two vacuum pumps of either liquid ring or rotary vane type. There will also be two sewage discharge pumps an electrical control panel and probes and pressure switches mounted on the vessel to control the equipment. Redivac can supply an optional Interface Valve Monitoring system with a display panel sited in the vacuum station.
4. Is a standby generator required for a vacuum sewerage system?
If it is expected that power failures will be of a duration shorter than a recommended four hours then standby generation will not be required as the system will be designed with retention built in. However, if power failures are likely to be in excess of four hours then standby generation may be required, alternatively storage volumes could be increased by using larger sumps or increasing the number of collection sumps.