LTA - Tryckavlopp för småhus

Vad är ett LTA-system?

Tryckavloppssystem Ett tryckavloppssystem består av uppsamlingstankar, tryckgenererande utrustning och rör som bildar ett grenat nät.* *SS-EN 1671 standard Just to make sure that we are on “the same page”

Olika huvudtyper av avloppssystem Traditionellt självfallssystem Rör med stor diameter (150-600 mm) med kontinuerlig lutning till nästa pumpstation Ibland omöjligt att anlägga (t ex i motlut) Stor kapacitet Mindre utrustning att underhålla Högre installationskostnader Mer omfattande anläggningsarbeten (för ledningsschakt och pumpstationer) Tryckavloppssystem (LTA) Klenrörsledningar (40-110 mm) som läggs strax under frostfritt djup eller grundare med isolering och värmekabel Läggs på konstant djup från markytan och följer ytans kontur Liten påverkan på miljön vid utbyggnad Ofta >50 % lägre installationskostnad jämfört med självfallsystem Just to make sure that we are on “the same page”

Många möjligheter med tryckavlopp Vid högt ställda miljökrav Utbyggt kommunalt VA i spridd bebyggelse Besvärliga topografiska förhållanden Vid höga grundvattennivåer Konvertering från säsongs- till permanentboende Exploatering av nya bostadsområden

Enstaka fastigheter kan anslutas Huvudledning Benefits One household per station Pumpstation Rörsystem Servisledning från anslutningspunkt till fastigheten

Flera fastigheter bildar ett system Huvudledning Benefits One or several households/buildings per pump station Pumpstation Rörsystem Servisledning från anslutningspunkt till fastigheten

Frågor att beakta vid utformning av LTA-system Fritidsboende eller permanentboende Topografi Antal fastigheter och hushåll Dimensionerande vattenflöden Behov av framtida expansion av LTA-systemet Utvecklingsplaner och etapper för området Behov av extra tillförlitlighet (stationer med dubbla pumpar) Olika pumptyper (centrifugal- eller förträngningspumpar) Antal pumpar i samtidig drift Tillräcklig vattenhastighet för att undvika sedimentation i ledning Tillräcklig omsättningstid för att undvika dålig lukt Strategier för styrning, övervakning och underhåll Vacation home or residences: A daily through flow decrease the risk for odour and sediments in the pipes. Automatic or manual water flushing can be required in vacation houses with long pipes to dilute and reduce the retention time for the wastewater. Flushing post and / or shut off valve at the boundary of the building plot are other measures that reduce the risk for a malfunctioning pumping system. Number of households and Number of pumps in simultaneous operation: The number of households is one parameter that determines how often several pumps in the system run simultaneously. This determines the pressure and flow in the pipes thus the velocity of the wastewater in the pipe. Once every 24 hours the velocity should reach at least 0.7 m/s (2 feet/s in the US) in all pipes in the system. Several households connected to one pump station increases the flow from that pump station (the pump runs more frequently) which also can be beneficial to reduce the retention time. Volume of wastewater: The volume of wastewater in combination with the start at stop levels in the tank determines how often the pump will run. A common estimation in Europe is that in average will 3.5 person produce 180 wastewater every 24 hours (100l/s in Germany). A typical running time for a pump is 10 minutes every 24 hours. The amount of wastewater in combination with the pipe volume determines the retention time, V / Q, of the wastewater. The standard EN1671-1:1997 recommends less than 8 hours to prevent odour and corrosion problems. Future extension of the PSS system and Area development sequence and schedule: Further area development might require larger main pipe to have capacity to receive also the future flows. Topology: Pumping uphill from a household to the receiving main pump station is no problem, just make sure the pump has sufficient head (at required flow to maintain the speed, 0.7 m/s, of the water in the pipes), geodetic head plus dynamic head from the friction losses. An elevation pipe peak should be considered carefully as vacuum will occur at larger elevations than approximately 8 meters. Vacuum can cause additional friction losses and might require a higher pressure class. A siphon breaker can be required when the outlet is at lower elevation than the pump station. In its simplest form it is just a hole in the pressure pipe in the pump station. Need for extra high reliability: For pump station where overflow can cause severe damage such as in sensitive environments, bathing places etc, a double pump station might be required to reduce the risk for flooding if one pump stops from clogging of unwanted objects etc. Monitoring, control and maintenance strategies: The simplest pump station monitoring is an audible alarm or flashing light that notifies the house owner to check the pump station. The most advanced monitoring is a telemetric surveillance (at distance) to send out a repair team when required depending on the seriousness of the alarm. Which strategy that should be applied depends on who is responsible for the wastewater transport but also on the level of service needed, requested by the house owner.