Low-Pressure Sewer System ( LPSS )

General Description: The VORTEX Grinder Pump system is designed to function as a part of a low-pressure sewer system. These systems are designed to operate where implementation of a conventional system is impractical, uneconomical or otherwise not feasible. By definition, a low pressure sewer is a small diameter pipeline that follows the profile of the ground, buried in a shallow trench. Each home uses an individual grinder pump to discharge waste to the force main. The VORTEX Grinder Pump is specially designed to grind the solids in wastewater to slurry, similar to a garbage disposal. The positive displacement progressive cavity pump technology of the VORTEX system is the ideal choice to reduce the waste and then facilitate its transport across distances of up to a mile and over terrain that can vary as much as 138 feet. The VORTEX pump is engineered to provide years of trouble-free, reliable service for this application. In addition, the LPSS traditionally constructed of PVC and HDPE piping, will provide years of service collection, free of I & I, and allow the large capitol cost of treatment to be used to treat the waste from houses and not infiltration.

A low-pressure sewer system (LPSS) is not the ecnomical solution to all sewer collection problems. If the front footage of the sewer area is 30' to 60' and an outfall has no grade problems, a gravity sewer is the most economical way to collect the sewage and transport it to the treatment facilities. However there are many situations when LPSS is the best way to go. Some examples of appropriate design for LPSS are listed below:

1. If an extremely envirinmentally sensitive area or an area of great importance lies between an outfall and the sewer area, the units can be serviced by VORTEX pump, each tying into one main and the main directionally drilled under the sensitive area. This in turn can be connected either to an exiting gravity or pressure sewer. With the high head capacity of each Vortex pump, no additional pumping station is needed.

2. To sewer an existing area in which the lot fronts are in excess of 150', the cost advantage of 2"-3" collection pipe ($8 -$12/foot installed) as compared to 8" gravity ($18-$100/foot installed) makes the LPSS a cost effective method of design. The cost differential in piping must overcome the grinder pump istalled price of approximately $5000 per unit.

3. If there are partial lots in an area requiring sewage systems requiring a gravity depth in excess of 20' because of terrain, while the remaining lots require a sewage system with an 8' depth gravity line, the design engineer can be cost effective with a design of 8' depth (cost $30/foot installed) and installing several Vortex grinder pumps to sewer the lots ($5000/unit) in contrast to running the gravity line at a depth in excess of 20" (cost$100/foot installed).

 

 

4. Often times a grinder unit may correct a particularly troublesome problem. An example of this was accomplished recently in Florida. There was 1 unit connected to a MH, (man hole), in an access ramp on I-95. The MH was 35' deep, having been necked up at the time of road construction, in the center of the ramp, the pipe going into the MH collapsed. A 2" discharge line was run into the existing sewer and drilled through the collapsed pipe into the MH and a grinder pump then serviced the unit, eliminating an extremely costly repair to the existing sewer.

5. Extremely flat or rugged terrain can make the LPSS cost effective. Both types of terrain can cause the necessity of multiple pump stations. Besides the cost of aquisition of real estate for pumping stations and the cost of construction ($100.000-$300,000) and the cost of deep gravity sewers at ($20' + $100/foot installed), often times the small diameter force mains ($9-$12/ft installed) + the cost of each individual grinder ($5000/unit) is the most cost effective and should be investigated by the design engineer. Not all sites are designed for the LPSS, but cost savings and land usage dictates the Design Engineer to investigate this option.

6. All sewer authorities have run into an area where they dread an installation because the conventional methods of construction, causing all the disturbance inherit in this type of construction, make the installation a nightmare. Directionally drilled 2" force mains eliminate 90% of this disturbance and just simply make everyone's life better. Installing Vortex pumps is an answer to their prayer. Another cost savings to developers is the ability to defer the on-lot pump costs until the site is built. This is especially advantageous in areas of slow build up.

7. All authorities have run into situations where they just run out of cover for gravity lines and are forced to install a terminal MH before the last few lots receive sewage systems. A small LPSS system can be the appropriate design, cost effective system than the costly pump station.

8. Many low lots have remained on septic systems in the past, simply because the house lot was too low to be sewered. A single Vortex pump lifting the sewage to the existing gravity lines is the answer. In other situations the unit sewered was just too far away from the main to allow a 1/4" / foot fall service line to be used from the init to the sewer main. Again, a single Vortex pump is the answer.