Installation of a pumping septic tank: what you need to know before installation

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Installation of a pumping septic tank: what you need to know before installation

A pumping septic tank is a device you simply cannot do without in any location where gravity is not sufficient to carry away wastewater to the public sewer or to a home septic tank. In practice, this means basement bathrooms, underground garages with a shower, recreational buildings located on land that is lower than the surrounding area, or even entire houses where the sewer connection is located at a higher level than the floor. A properly designed and professionally installed tank will serve you for decades without problems. An improperly designed and hastily installed tank will cause problems from the very first year — whether in the form of bad odors, pump failures, flooding, or unnecessarily expensive repairs.

This article is intended for anyone planning such an installation — whether you are doing it yourself or simply want to communicate effectively with your plumber. We will go through the entire process from the first decisions through the selection of the correct tank size, excavation preparation, installation, pump connection, and commissioning. We will also include specific numerical values, dimensions, calculations, and examples from typical customer projects.

When a pumping septic tank is really needed

The first question you should ask yourself even before any planning is: do I really need a pumping septic tank, or would another solution be sufficient? From experience, I know that customers often underestimate this question in both directions — some buy an expensive pumping system where a gravity solution would be enough, while others try to use gravity to solve situations that are physically impossible.

The basic rule is simple: if the waste pipe from your home cannot have sufficient slope toward the sewer system or septic tank, you need pumping. The minimum slope for a DN 100 gravity pipe is 2% (i.e., 2 cm height difference per meter of length). If you have a basement bathroom located 15 meters from the main sewer connection and the connection or inspection chamber is located 30 cm above the basement floor, gravity is not sufficient — a simple calculation shows: you need 30 cm + (15 m × 2 cm) = 60 cm height difference, but you only have 30 cm in deficit.

Other typical situations from practice, where a pumping septic tank is not just an advantage, but a necessity:

Garden cottages and weekend homes built on a slope, where the terrain slopes away from the public sewer
Detached houses with a double garage built below ground level, where a floor drain or sink is planned
Restoration of historical buildings, where it is not possible to lower the level of the sewer connection
New constructions on flat plots, where the sewer connection is located deeper, but the internal sewer system is routed higher due to an insulated floor
Wellness facilities, swimming pool rooms, and basement bathrooms

If you are unsure whether your situation falls into this category, read the article How to choose a chamber: water meter, inspection, or pumping? in our Knowledge Center, where these scenarios are discussed in more detail.

Selecting the correct size and type of chamber

The market offers pumping septic tanks in various diameters and heights. For single-family homes and smaller buildings, chambers with an internal diameter of 1000 mm, 1300 mm, or 1600 mm are most commonly used. The choice depends on several factors: the amount of wastewater generated, the number of connected appliances, the need for access to the pump for service, and the handling space within the chamber.

A chamber with a diameter of 1000 mm is the most compact and is suitable for simple applications with one or two sources of wastewater (e.g., one basement bathroom). It does not allow entry of a worker inside, which complicates pump maintenance when the chamber is buried deeper. A chamber with a diameter of 1300 mm already provides an acceptable handling space and can be comfortably accessed from above when the depth is up to 1.5 m. A chamber with a diameter of 1600 mm is intended for larger loads, multiple inlet pipes, and situations where regular physical maintenance from inside is expected.

In our category Chambers and tanks, you will find proven complete sets: for example, Pumping septic chamber MIDI 1300×1000 for blackwater and sewer is an ideal solution for a standard single-family home with one basement bathroom, while Pumping septic chamber MIDI 1600×1000 – complete set for wastewater can handle a larger load, such as two bathrooms in the basement or a wellness room with a bathtub, shower, and washing machine at the same time.

When selecting the size, always calculate the buffer volume of the chamber as well. The pump does not activate for every glass of water poured into the sink — it operates in cycles. The buffer volume must be large enough to prevent the pump from starting too often (at least 6–10 starts per hour is technically acceptable, ideally less). For a standard basement bathroom (shower + toilet + sink), a buffer volume of at least 150–200 liters between the pump's on and off levels is recommended.

The topic of dimensions is discussed in more detail in the article What chamber size do I need: 1000 vs. 1300 vs. 1600 mm diameter in our Knowledge Center.

Project preparation and permits

Before starting any earthworks, you need to address the administrative side of things. A pumping septic tank is part of the sewer connection or internal sewer system and is therefore subject to building regulations.

In practice, if you are installing the chamber on the land of a single-family home as part of the internal sewer system or as part of connecting to the public sewer, it is usually sufficient to report a minor construction or a simple construction under Act No. 50/1976 Coll. (Building Act) and the relevant implementing decrees. However, if it is a new construction or a major renovation with a new sewer connection, you will usually need a building permit or at least a statement from the public sewer operator (municipality, water utility company).

Practical steps before implementation:

Verify the existence and location of engineering networks (gas, electricity, water supply, telecommunications) at the site of the planned excavation – order a passportization or request statements from network operators.
Consult with the relevant municipal office or building authority to find out whether your case requires a permit or just a notification.
If you are connecting to the public sewer system, request the technical connection conditions from the sewer operator – they will specify the maximum flow rate, connection depth, and requirements for the material of the discharge pipe.
Have a simple layout (scheme) prepared showing the manhole, the route of the discharge pipe, and the connection point to the sewer lateral.

Excavation preparation: dimensions, depth, and bottom

The excavation for the pumping manhole must be sufficiently spacious to allow you to properly place, level, and backfill the manhole. As a basic rule, the excavation should be 30–40 cm wider on each side than the outer diameter of the manhole. For a manhole with an outer diameter of approximately 1100 mm (i.e., 1000 mm internal plus wall thickness), the excavation should be at least 1700–1800 mm in diameter or a square excavation of 1800×1800 mm.

The depth of the excavation depends on the depth of the manhole installation. This depends on two factors:

Height of the incoming pipes: Wastewater must flow into the manhole by gravity – the inlet pipe must have a sufficient slope (minimum 2 %) from the last fixture to the manhole. If your WC is located 5 meters from the manhole in the basement, a 2 % slope means a 10 cm height difference. The inlet pipe collar must open above the maximum water level in the manhole.
Frost depth: In Slovak conditions, it is given as 80–120 cm below ground level depending on the region. The manhole itself is not directly threatened by frost, as it is a buried object with a constant ground temperature, but the discharge pipe leading outside must be laid below the frost depth. We will discuss this topic in more detail in the article Manhole burial depth: how to correctly place the manhole below the frost level.

The bottom of the excavation must be carefully prepared. Although plastic manholes are self-supporting, an unstable bottom can cause their settlement or tilting, which can compromise the tightness of the joints. The procedure for preparing the bottom of the excavation:

Remove unsuitable, soft, or organic soil (humus, peat) until you reach a stable layer.
Apply a gravel-sand backfill layer of at least 150 mm thickness (fraction 8–16 mm or similar) and compact it thoroughly.
Place a concrete leveling layer of 100–150 mm thickness on the compacted layer, or a concrete slab according to local geological conditions (groundwater level, soil bearing capacity).
Allow the concrete to sufficiently harden (at least 48–72 hours at normal temperatures) before placing the manhole.

Manhole installation and pipe connection

Once the excavation with the concrete slab is prepared, you can proceed to the actual installation of the manhole. Plastic pumping manholes are lighter compared to concrete ones – a manhole with a diameter of 1300 mm and a height of 1000 mm usually weighs 40–80 kg depending on the manufacturer, which can be handled by two workers without mechanization.

Step-by-step installation procedure:

Lowering the manhole into the excavation: Lower the manhole carefully to avoid damaging the collars, seals, or the bottom. Never lower the manhole using the auxiliary handles intended only for maintenance, but using the body of the manhole.
Leveling to the water level: Use a spirit level to check the horizontal alignment of the top edge of the manhole in at least two perpendicular directions. A deviation greater than 5 mm per meter can cause problems with the tightness of the cover and the function of the floats.
Connecting the inlet pipes: Wastewater flows in by gravity through the collar in the wall of the manhole. The collars are standardly equipped with rubber seals. Insert the pipe into the collar to a sufficient depth of the socket joint (at least 50–70 mm). Ensure that the inlet collar opens at least 10–15 cm above the maximum pumping level – this prevents reverse suction.
Connecting the discharge pipe: The discharge collar is on the opposite side or at the top of the manhole wall. A check valve must be built into the discharge pipe (in the discharge branch of the pump, not in the manhole) and a shut-off valve is also recommended for the case of pump replacement. The discharge pipe PE or PVC is led to the sewer lateral or inspection manhole, and must be laid below the frost depth.
Backfilling the manhole: Backfill with gravel-sand (fraction 4–8 mm or 8–16 mm) in layers of maximum 30 cm, compacting each layer thoroughly with a vibrating tamper around the manhole. The plastic manhole is self-supporting, but uneven lateral pressure can cause deformation.
Refilling the excavation: Refill the upper part of the excavation with the original soil or gravel-sand according to the nature of the surface (garden, paved area, communication).

Backflow protection

One of the critically important components of every pumping installation is backflow protection. When the pump turns off, the column of water in the discharge pipe would immediately flow back into the manhole without a check valve. This would not only waste energy (it would have to be pumped again), but would also lead to water hammer and premature wear of the pump.

The check valve is installed directly on the pump discharge nozzle or in the first horizontal section of the discharge pipe. For larger manholes with gravity-fed flushes from siphons and toilets, it is also necessary to consider protection on the inlet pipes – in the event of a sewer network failure or extreme rainfall, water may flow under pressure in the opposite direction. In such cases, it is appropriate to use a manhole base with a check valve 400/160, which is specifically designed for these situations. The topic is discussed in detail in a separate article in our Knowledge Center: Backflow protection: when do I need a check valve in a manhole?

Installation of the pump and control system

The heart of the pumping manhole is the submersible pump. For wastewater, only pumps designed for sewage should be used, capable of pumping sludge and fibers (toilet paper, sanitary products, etc.). Never use standard clean water drainage pumps – their mechanical seals and rotor are not structurally suitable for this purpose.

Basic parameters to consider when selecting a pump:

Flow rate [m³/h or l/min]: Must cover the maximum simultaneous discharge from the connected fixtures. A typical basement bathroom (toilet + shower + sink): expect a peak flow rate of around 2–3 l/s, which is 7–11 m³/h.
Head [m]: The sum of the static head (the height difference between the pumping level and the connection point) and the dynamic losses in the pipe. For example: static head 3 m, PE32 pipe length 20 m → total losses approx. 1.5–2 m → required head at least 5 m. Allow a reserve of 20–30 %.
Passage of solids: Minimum 35 mm for toilets, ideally 50 mm for safe operation.
Protection class (IP): For submersible pumps in a manhole, at least IP68.

The control system consists of floats (hydraulic level switches) and a control box with fuses. A standard setup includes at least two floats: one for the pump on level and one for the pump off level. It is recommended to add a third float as an emergency alarm – in case of maximum level exceeded (e.g., in the event of a pump failure), it triggers an acoustic or visual alarm or sends a message via a GSM module.

Float placement:

Emergency float: 10–15 cm below the inlet pipe collar (in case the pump fails and the manhole would overflow)
ON float: 20–30 cm above the bottom of the manhole (depending on the storage volume)
OFF float: 5–8 cm above the bottom of the manhole or above the pump suction level

The electrical installation must be carried out in accordance with STN 33 2000-7-701 (bathrooms and showers) and other applicable standards. The electrical box with switch, fuses, and float relay is installed outside the manhole, in a dry and accessible location. The cable to the manhole must be run in a protective conduit and its penetration through the manhole wall must be sealed.

Discharge pipe: material, routing, and laying

The discharge pipe operates under pressure – this is a fundamental difference compared to gravity-fed waste pipes. You must therefore use pressure pipe, not standard PVC gravity pipes for sewerage.

The most commonly used materials for discharge:

PE100 SDR 17 or SDR 11: Pressure PE pipe is flexible, corrosion-resistant, and can be butt welded or connected with electrofittings. For single-family homes with a head up to 20 m, SDR 17 (working pressure PN 10) is completely sufficient.
PVC-U pressure pipe: A cheaper alternative, but less resistant to impacts and temperature fluctuations. Suitable for shorter routes in a protected environment.
Stainless steel or polypropylene flanged pipes: Used in interiors (e.g., in the basement of a house before exiting to the ground).

The dimension of the discharge pipe is selected so that the flow velocity of the wastewater is at least 0.7 m/s (self-cleaning velocity – prevents deposition of solids) and at most 2.5–3 m/s (at higher velocities, hydraulic losses and noise occur). For a typical pump with a flow rate of 8 m³/h: pipe DN 40 (40 mm) → speed approx. 1.8 m/s – suitable. Pipe DN 50 → speed approx. 1.1 m/s – ideal.

The laying of the discharge pipe in the ground must be below the frost depth (min. 80–100 cm depending on the region). The pipe is laid in a sand bed of at least 100 mm thickness and backfilled with sand to a height of at least 200 mm above the pipe top. All direction changes are made with fittings, not by bending the pipe (PE can handle bending, but it unnecessarily creates local losses).

Pumping manhole combined with a water meter manhole or inspection manhole

In practice, we sometimes encounter situations where the need for a water meter manhole and a pumping manhole coincides on one plot. In some cases, it is economically more advantageous to solve this with two separate manholes. If you plan to install a water meter manhole, our range includes, for example, Round water meter manhole PP 1300×1000 plastic self-supporting or for larger installations Round water meter manhole PP 1600×1000 plastic self-supporting. Combining functions into one manhole (water meter + sewer valve + check valve) saves space, but in the event of a pump failure or backflow of wastewater, you expose water supply equipment to undesirable contact. From a hygiene and operational point of view, I recommend separation.

Common installation errors and how to avoid them

Over the years of working with customers, I have seen dozens of cases where the installation of a pumping shaft went well, but also dozens of cases where something went wrong. The most common errors are:

1. Underestimated lift height of the pump

The customer buys a pump with a declared maximum lift of 8 m, but forgets that this value applies at zero flow. At a real flow of 6 m³/h, the same pump lifts water only to 5 m. If the discharge line is 6 m long, the pump simply cannot push the waste through. Always look at the pump curve (Q-H diagram) and choose a pump so that your operating point lies in the optimal part of the curve.

2. Incorrect float settings

The OFF float set too high → the pump runs dry, the impeller and mechanical seal are damaged. The ON float set too high → the buffer volume is too small, the pump switches on too often (hydraulic shock, rapid wear of starting capacitors). Set the correct level difference according to the manufacturer's recommendations.

3. Missing or poor check valve

Using an unsuitable check valve (e.g., a light valve for clean water) on the discharge of sewage. Fibers and sludge clog the valve in the open position, water flows back, the pump runs in vain. Always use check valves certified for sewage, ideally ball or membrane type.

4. Insufficient shaft size

Too small a buffer volume in the shaft → the pump switches on 30–50 times per hour during showering → motor winding burned out within two years. It is better to buy a shaft with a diameter one size larger than to later pay for a new pump.

5. Poor sealing of pipe penetrations

Leaky pipe penetrations through the shaft wall → groundwater enters the shaft (the shaft fills with groundwater, the pump runs unnecessarily) or sewage leaks out (soil contamination, bad smell). Each penetration must be installed with a rubber seal and sufficient pipe insertion depth.

6. Lack of emergency alarm

One of the most expensive oversights. If the pump fails on a Friday evening and you are away for the weekend, by Monday you will have a flooded basement. A third float or a GSM alarm is worth it in every installation without exception.

Maintenance and operation after commissioning

A pumping sewer shaft is not a device that you install and forget. It requires regular – but fortunately simple – maintenance.

Recommended inspection frequency:

Once every 3–6 months: Visual inspection of float movement, manual pump test, check if the check valve seals (after pump shutdown, the water level should not rise quickly due to backflow from the discharge).
Once a year: Remove the pump from the shaft, flush the shaft with high-pressure water, inspect the condition of the rotor and mechanical seal, clean the strainer if the pump is equipped with one.
Every 5 years: Complete inspection including electrical installation, replace floats if they show stiffness or corrosion, check the condition of the discharge pipe and check valve.

Never use aggressive chemical cleaners, acids or alkalis in the shaft – they will damage the pump seals and biological processes in the sewer. For basic cleaning, high-pressure water is sufficient.

The topic of faults and their solutions is covered in the article Common faults of shafts and pumping units: causes and solutions in our Knowledge Center.

Special situations and advanced topics

High groundwater level

If the site is located in an area with a high groundwater level, a plastic shaft may float out of the excavation when empty – the plastic body is lighter than the displaced water volume. In such a case, the shaft must be anchored – either with a concrete foundation slab and anchor brackets or with a weight in the form of a concrete collar around the lower part of the shaft. Buoyancy calculation: shaft volume [m³] × 1000 kg/m³ = maximum buoyancy force in kg. Anchoring must be dimensioned to at least 120 % of this value.

Shaft in the garden vs. shaft in the garage

A shaft located indoors (basement, garage) has different requirements than a shaft outdoors. Indoors, you must address ventilation – a sewage shaft produces hydrogen sulfide and other gases that must be vented. The shaft must have a vent pipe extending above the roof (as with standard sewer ventilation). The cover opening must be sealed (to prevent odors), but also allow easy access for service.

Duplex (two pumps)

For critical applications (restaurant, business, home where no interruption in operation is possible), a duplex is installed – two pumps in one shaft. They alternate automatically (even wear), and in case of failure of one, the other takes over the full load. This configuration requires a larger shaft diameter (minimum 1300 mm, ideally 1600 mm) and a dual-channel control unit.

Most Frequently Asked Questions (FAQ)

Do I need a building permit for the installation of a pumping chamber?

It depends on the specific situation. If it is part of the internal sewage system of a family house during reconstruction without changing the purpose of the building, it is usually sufficient to report minor construction or record it in the construction diary. In the case of a new building or connection to a new public sewage connection point, you will most likely need a building permit and a statement from the sewage network operator. Always consult with your local building authority in advance – each municipality may have slightly different requirements.

What is the lifespan of a plastic pumping chamber and pump?

A plastic chamber body made of PP or PE has a lifespan of 50 or more years when properly installed and backfilled – it is not something that would typically require replacement. The pump is a different matter: a quality submersible wastewater pump should last 10–15 years with regular maintenance and proper float settings. Floats and membranes in the check valve should be replaced preventively every 5–7 years, without waiting for a failure.

How much electricity does a pumping chamber consume?

A typical submersible pump for a family house has a power consumption of 0.37–1.1 kW. With a real daily operation of 15–30 minutes (for a family of four), this amounts to a consumption of 0.1–0.55 kWh/day, which totals 35–200 kWh per year. At a rate of 0.25 €/kWh, this results in annual costs of 9–50 €. In terms of energy consumption, pumping is not a significant burden for a household.

Can I connect rainwater from the garden to the pumping chamber?

Absolutely not. A pumping chamber for blackwater is designed for different volumes and water composition. A sudden influx of rainwater could flood the chamber, overload the pump, and, if connected to the blackwater sewer, violate connection conditions (network operators prohibit this and mixing blackwater and rainwater can result in a fine). Rainwater belongs in a soakaway pit, retention tank, or a separate rainwater drainage system.

How deep should the discharge pipe be buried in the ground?

At least below the frost line, which in Slovakia is defined regionally according to STN 73 6005: in lowlands (Podunajská nížina, Záhorská nížina) 800 mm, in most of central Slovakia 1000–1100 mm, and in higher elevations and the north up to 1200 mm. If for technical reasons the required depth cannot be achieved, the pipe must be thermally insulated.

What to do if the chamber smells inside the house?

An odour from the pumping chamber into the interior usually indicates one of the following problems: missing or damaged ventilation pipe of the chamber, a leaking cover, dried-out traps on the inlet pipes (if present), or a failure in the sealing of the penetrations. Check the ventilation route: every chamber must have a vent pipe extending at least 500 mm above the roof and must not be routed into the HVAC system or into the interior. At the first sign of an odour, also check whether the chamber cover is cracked or improperly seated.

Conclusion: an investment that pays off when done correctly from the start

A pumping sewage chamber is one of those construction elements where mistakes become apparent only after some time – and then repairs are always more expensive and complicated than a correct initial installation. Whether you choose the compact unit MIDI 1300×1000 for a standard basement bathroom or the more robust unit MIDI 1600×1000 for higher loads, it is essential to follow the correct procedure from the excavation preparation, through the installation and tight connection of the pipes, to the proper setting of the pump and its control.

Do not be tempted by shortcuts or savings in the wrong places – for example, the quality of the pump, sealing of penetrations, or emergency alarm. A pumping chamber operates 365 days a year, so it is important to get it right from the beginning.

Do you have a question about this topic?

Having trouble deciding or dealing with a specific situation in your home? Write to us – we are happy to help.