How to Choose a Submersible Pump? Drainage, Sewage and Borehole Pump Guide (2026)

Is your basement flooded, your septic pit overflowing, your well pump failing, or does the pump in your drainage pit clog every time it rains? Most of these problems come from choosing the wrong submersible pump. Using a clean water pump in a septic tank, or buying a model without enough head, burns the pump out quickly. This guide explains step by step how to choose a submersible pump, the difference between a drainage pump and a sewage pump, and which Pedrollo submersible pump is right for which job.

Short answer: choose a submersible drainage pump for clean or slightly dirty water (rainwater, flooded basements, pools), a submersible sewage (waste water) pump for sewage, septic tanks and waste water with solids, and a submersible borehole pump to draw clean water from a well. Three values decide the right model: the size of solids in the water (mm), head (m) and flow (m³/h).

Quick Selection Table: Which Submersible Pump for Which Job?

What Is a Submersible Pump and How Does It Work?

A submersible pump combines the motor and pump body in a sealed unit that works fully immersed in the liquid. Because it does not need to lift water by suction, it has no suction-lift limit: it pushes the water up. The surrounding water also cools the motor. That makes submersible pumps the most efficient choice for basements, pits, septic tanks and wells, where pumping from the surface is difficult.

Step 1: Identify the Type of Water and the Size of Solids

The most common mistake is using a clean water pump in sewage or muddy water. The largest solid the pump can pass must be bigger than the solids in the water:

Step 2: Calculate the Head

Head shows how high and how far the pump can deliver water. For a first selection, this simple calculation is enough:

Required head ≈ Vertical height + About 10% of the horizontal pipe length + Safety margin

Example: to pump water from a basement pit to a drain 4 metres higher through 30 metres of horizontal pipe: 4 m + 3 m (10% of 30 m) + 2 m safety margin ≈ 9 m. Choose a pump that delivers at least 9 m, and make sure this point is not too close to the pump's maximum head, because flow drops as you approach the maximum. The "Max. Head" value in the product tables is the head at zero flow.

Step 3: With Float, Built-in Float or Without Float?

• With float: the pump starts when the water rises and stops when it is drained. Ideal for unattended places such as basements and pits.
• Built-in float (GM): the float is inside the pump, so there is no risk of the cable catching on the walls of a narrow pit.
• Without float: controlled by a panel or a separate level switch; preferred for large stations and twin pump systems.

Step 4: Choose the Impeller Type and Body Material

• Vortex (recessed) impeller: the impeller sits back inside the body, so solids pass without touching it. The most clog-resistant type and the safe choice for sewage.
• Channel impeller: higher efficiency and head; preferred in waste water stations.
• Technopolymer body: light and economical; enough for household drainage.
• Stainless steel body (RX, VX-ST, BC-ST): long life in hot, salty or aggressive water.
• Cast iron body: for heavy duty, sludge and industrial applications.

Step 5: Check the Power Supply

Models with an "m" in the name (e.g. VXm, RXm, BCm) run on single-phase 220 V; models marked "(TRF)" run on three-phase 380 V. Homes usually use single-phase models, while industry and large buildings use three-phase models.

Pedrollo Submersible Pump Prices (November 2026)

At Isımatik, all Pedrollo submersible pumps are sold at list price excluding VAT; prices are shown on the site in Turkish lira at the daily exchange rate. Series starting prices:

For all models, see our Submersible Drainage Pumps, Submersible Sewage and Waste Water Pumps and Submersible Borehole Pumps and Motors categories. Prices are list prices at the time of publication; the current price is shown on each product page.

6 Things to Watch During Installation

1. Size the pit correctly: use a pit wide enough for the float to move freely; choose a built-in float (GM) model for narrow pits.
2. Keep the pump above the sludge: do not stand the pump directly in mud; place it on a firm base.
3. Fit a check valve: a check valve in the discharge line stops water flowing back when the pump stops and prevents unnecessary cycling.
4. Do not reduce the pipe size: the discharge pipe should not be narrower than the pump outlet; otherwise flow drops and sewage pumps are more likely to clog.
5. Never lift by the cable: always use a rope or chain to lower and lift the pump; hanging it by the cable damages the seal.
6. Respect the immersion depth: every model has a maximum immersion depth (usually 5–10 m for drainage pumps), which must not be exceeded.

Frequently Asked Questions

What is the difference between a drainage pump and a sewage pump?

A drainage pump is for clean or slightly dirty water and passes small solids (usually up to 10 mm). A sewage pump has a wide-passage impeller that can pump sewage and waste water containing solids up to 40–50 mm.

Which submersible pump should I buy for a septic tank?

For household and apartment septic tanks, the vortex-impeller Pedrollo VX is the most clog-resistant option. If the waste water must travel far or through a small pipe, choose the Tritus grinder pump.

How high can a submersible pump lift water?

It depends on the model: drainage pumps usually deliver 7–27 m, the multistage TOP MULTI 27–42 m, and deep well pumps more than 300 m. When choosing, make sure your calculated head stays below the pump's maximum value.

What happens if a submersible pump runs dry?

A submersible pump's motor is cooled by the surrounding water; running dry for long makes it overheat and damages the seal. Models with a float stop the pump automatically when the water level drops, preventing this risk.

Is the deep well pump sold with a motor?

The Pedrollo 4SR series is sold as a pump end without motor; a Pedrollo 4PD submersible motor of the right power is selected separately. Send us your well depth and the flow you need, and we will match the pump and motor for you.