The PITVAQ (i.e. the eVac Mk5) incorporates a 7 hp petrol engine (previous models were fitted with electric motors) and the vacuum tank is made using steel. This petrol engine makes use of the PITVAQ possible in places with either no electricity or an erratic electricity supply. The use of steel for the vacuum tank makes it easier to manufacture and to repair. This makes local manufacture possible in virtually any place where there is a steel fabrication workshop with basic competency. Both of these changes have made the PITVAQ much more widely applicable and thus a more commercially viable product.
The adjustments to create eVac Mk4 were made as a result of feedback from teams using the eVac on a regular basis for emptying latrines. Most notably, the eVac Mk4 included a stand for the vacuum tank, elevating it above the ground so that it could be drained via a discharge valve. The tank had a ball valve installed on the bottom so that sludge pumped into the tank could be removed via the valve into a bin/container that was easier to transport. This configuration was first used by Pit Vidura in Kigali, Rwanda, who were aiming to improve efficiency and their business model. This addition also improved the hygiene of the operation, as the vacuum tank did not need to be carried and the contents did not need to be poured out. The Mk4 also incorporated a trash screen that could be attached to the end of the sludge hose as well as a detachable portion of the sludge hose to make hose transport more hygienic.
The biggest change from 2015 to 2016 was to convert the pump chassis to a wheelbarrow arrangement to improve manoeuvrability. By providing a single large wheel at the front of the chassis, the machine was easier to manoeuvre through narrow, windy passages and over uneven terrain. This was done without increasing the width of the chassis. The eVac Mk3 was the most widely and regularly used, which allowed for consistent feedback contributing to practical improvements of the eVac.
The eVac Mk1 was the first iteration following PID’s initial research on pit emptying devices with the Water Research Commission. This version set the basis of the eVac technology, which included an electric motor, a vane pump, and vacuum tank. The design process required PID to develop a vacuum tank that could withstand a 95% vacuum and still meet the eVac’s goal of being flexible and transportable by a small emptying team. The eVac Mk1 also included protection for the pump from sludge and moisture using both a floating ball valve and a moisture trap.
