The lift pump is the driving force of a lifting stationwhose role is to temporarily store a fluid before transporting it to a circuit located above. In the usual language of building and public works (BTP), the expression is used interchangeably to designate the hydraulic pump alone or the entire lifting device. Versatile, these devices are a great help for many jobs in the house and garden.
Features of sewage pumps
Lift pumps consist of an electric or thermal motor, driving one or more stages of turbines. The objective is to suck a fluid, at the lowest point of a flow by gravity, to push it back under pressure, towards a new distribution or spreading network. Mobile or fixed, the lifting pump is characterized by:
- Engine power, in Watts, which must be sufficient to compensate, without effort (risk of overheating), the pressure drops of the system. This is an essential criterion for ensuring the reliability and durability of the lifting device.
- The maximum allowable flow. Expressed in cubic meters per hour (m3/h), it must be compatible with the minimum values defined by the hydraulic requirements. The volume of fluid transported decreases proportionally with the height of the discharge column.
- The total head (HMT). Expressed in metre, this data indicates the maximum drop in level acceptable by the pump in normal use. It is conditioned by the discharge pressure, measured in bars and decreases with horizontal discharge length.
- The allowable grain size, defines the maximum acceptable diameter of suspended solids in the fluid. In our homes, it is clear water or waste water, more or less charged.
The sewage pumps used in domestic installations are generally of the submersible type (protection index ≥IP 44), with a low-power electric motor (between 250 and 1,500 W). They include a automatic contactor limiting the level of the fluid in which the pump is submerged. These installations must be directly connected to a circuit breaker dedicated, located on the main electrical panel, or placed outside on a distribution panel confined in a sealed cabinet, mounted on a base.
Lifting domestic water: which pump for which use?
Mobile pumps, in general, self-damping, are operational as soon as the turbine is submerged in water. These devices often include a float switch (or lever), ensuring automatic operation within a predetermined level range. Surface pumps, which are more specialized, operate in a closed circuit. Their range of activity can be automated or regulated according to the water level or within a pressure range (aquastat). Be careful, many of these pumps are destroyed if they run empty. For pumps for occasional use, requiring your presence during operating phases, a simple manual switch will do the trick, reducing the amount of the investment accordingly.
The material and the technique of the impellers of the lifting pumps, differ according to the granulometrythe consistency and the nature suspended solids in the water. It is important to respect these limits under penalty of breakage not covered by the guarantees.
1 – Closed, median or open single-channel impeller clear or load-limited waters
Pumps for lifting clear water, known as “vide cave“, are designed to suck up slightly abrasive impurities from 13 to 20 mm maximum. The pump body and the impeller are made of synthetic materialin soft stainless metal (cast aluminum, brass, etc.) or in abrasion resistant metal (bronze, cast iron, stainless steel, etc.), for sucking up muddy and sandy water. These pumps allow high flow rates, but they gradually decrease when the total head increases.
Areas of use for clear water pumps:
- lifting of rainwater, flooding or construction sites;
- watering, tank filling;
- draining swimming pools or tanks;
- transfers of lightly charged household water (hand basins, sinks, showers, bathtubs, etc.);
- pretreated water, at the outlet of sanitary settling devices (septic tanks, all-water tanks, etc.).
2 – Contaminated wastewater or sewage
Pumps intended to transport water loaded with hard organic matterup to 50mm in diameter (waste food, toilets, etc.), use wheels with technology vortex (or at free swirl), sometimes on several floors. These are pumps full passage of great reliability using a paddle wheel, the blades of which rotate, without backlash, in a cylindrical chamber. This compact and self-priming system, with silent operation, offers much higher efficiencies than centrifugal turbines. It limits vibrations, accepts gas mixtures and does not clog.
Areas of use for slurry pumps:
- all applications of the clear water model;
- lifting of raw toilet water;
- kitchen water containing waste.
3 – Wastewater loaded with ligneous or fibrous matter
Grinder pumps are suitable for lifting water laden with elements up to 80mm of diameter. They can be suitable for all the above uses, but their most remarkable advantage is to operate, without problems, in conditions that block other systems or clog the discharge pipes. To achieve this level of safety, the turbine at wheel tearembeds a fine fiber cutting device (wipestowels…) or materials organic harsh. Reduced in this way, these materials are easily absorbed by the turbine and circulate freely in the pipes.
The lifting station
In domestic installations, the lifting station (or lifting station) is mainly used for emptying appliances located in the basement, to transport waste water and sewage flowing below the level of all-at-l sewer or to connect wastewater treatment plants to their spreading devices. The devices of the lifting station are an integral part of the personal sanitation network. As such, they must comply with the standards in force and be contained in a tank sealed against air and runoff water. This equipment can be manufactured and arranged in a traditional way. Its conformity will be checked by the public non-collective sanitation service (SPANC) depending on your municipality, during the mandatory visit, commissioning. Manufacturers, for their part, offer prefabricated sets, ready to connect and plug in, of different volumetric capacities, perfectly compliant and homologated by the Ministry of Health.
Typical composition of the lifting station:
- 1 storage tank (concrete or polyethylene) to be buried outside or in the basement of a utility room. The capacity is adapted to the peak volume to be treated;
- 1 lift pump equipped with its level switch;
- 1 orifice of ventilation ;
- 1 cable pass waterproof;
- 2 connections (entrance and exit of effluents);
- 1 tableau control.
- weatherproof outdoor electrical cabinet;
- securities anti-overflow and/or lack of water;
- borne de ventilation ;
The specifics of the installation may justify the use of optional elements:
- check valvesto avoid pump loss and reflux;
- prefilter or screento retain impurities and oversized metal objects;
- regulation warning of overheating;
- stirrer, to avoid the solidification of deposits at the bottom of the tank, etc.
The upper hatch of the lifting station is located at the finished ground level, in order to facilitate checks, maintenance or replacement of internal elements. During installation, especially in wet or flood-prone areas, it is essential to lester la base from the lifting station, by a concrete slab of sufficient volume to prevent it from rising, like a cork, tearing off the pipes and electrical cables as it passes.
Treatment plant maintenance
The lifting station of a particular sanitation, well designed and correctly sized, requires little maintenance. The only intervention on the lift pump, itself, can come from a foreign body immobilizing the mechanism. It is most often a flexible and long object, rolled up in the turbine (cord, textile or plastic band, etc.), having escaped the pre-filtering. Removing it allows things to resume their course, without consequence. This incident illustrates the usefulness of thermal safety, preventing the motor from burning out, and of an overflow alarm, warning of the incident before flooding.
In routine, carry out 2 to 3 times a year, with a quick cleaning:
- loosen the sediment accumulated on the float or/and clean the probes;
- scratch them fat deposits possible, the walls of the pump and the tank;
- clean the pre-filters and the screen;
- rinse with clear water and empty the tank to eliminate the cleaning residues.
Very important and yet little-known precaution to the general public: before a long absence (several months), carry out a rinsing two rounds and drain imperatively the tank of the lifting station. This precaution will prevent the grease from hardening, permanently clogging mechanisms and pipes.