Domakihub How to Install a Sump Pump and Keep Your Basement Dry
A practical guide to choosing, fitting, and maintaining a sump pump in your home or rental property.
Reviewed by Domakihub home & decor pros · 2026-06-23 · 5 min read
A flooded basement or utility room can cause serious structural damage and mold problems — a particular concern for holiday rentals, hotels, and older homes across Greece where heavy winter rains or rising groundwater can overwhelm drainage. A sump pump is one of the most reliable ways to keep a below-grade space dry, and with the right preparation a qualified plumber can install one in a single day. The video above shows the full process from pit excavation to first test run; this guide walks you through each stage so you know exactly what to expect and how to talk to your contractor.
Why Sump Pumps Matter in Greek Properties
Many Greek homes, basement apartments, and ground-floor hotel utility rooms sit at or below grade. During the winter rainy season — especially in Attica, Thessaloniki, and coastal areas — groundwater can rise fast and enter through floor slabs or wall joints. A sump pump collects that water in a purpose-built pit and ejects it away from the building before it can cause damage.
Holiday rental owners in particular face high stakes: a flooded lower level mid-season can trigger cancellations, refunds, and lasting review damage. Installing a sump pump is a proactive investment that typically costs far less than a single flood claim.
What You Need to Know Before Work Begins
A standard sump pump installation has three main components: the sump basin (a cylindrical pit dug into the floor), the pump itself (submersible or pedestal), and the discharge pipe that carries water outside. You will also need a check valve on the discharge line to prevent backflow, and ideally a battery backup unit so the pump keeps running during power cuts — exactly when storms are worst.
The electrical connection for a sump pump must comply with local wiring codes. In Greece this means a dedicated, earthed 230 V socket, ideally on a circuit protected by a residual-current device (RCD). The socket installation or any modification to the consumer unit must be carried out by a licensed electrician. Your plumber and electrician should coordinate before digging begins.
How a Sump Pump Is Installed: 5 Key Steps
- 1
Dig and set the sump basin
The plumber selects the lowest point of the basement floor — usually a corner — and cuts through the concrete slab with an angle grinder or jackhammer. A cylindrical plastic or concrete basin (typically 45–60 cm diameter, 60–90 cm deep) is set into the hole and surrounded with gravel to allow groundwater to seep in freely. The rim is sealed flush with the floor and a tight lid fitted to prevent debris entry and reduce humidity inside the space.
- 2
Install the pump inside the basin
A submersible pump sits on a small platform or gravel bed at the bottom of the basin. The pump is connected to a vertical discharge pipe that rises out of the pit. A float switch — either a tethered ball float or an electronic sensor — is set at the desired water level; when water reaches that height, the float triggers the pump to turn on automatically. Check that the float moves freely and cannot snag on the basin wall.
- 3
Fit the check valve and route the discharge pipe
A check valve is installed on the discharge pipe just above the pump outlet. This one-way valve closes the moment the pump stops, stopping water from draining back into the pit and forcing the pump to restart unnecessarily. The discharge pipe is then routed through the basement wall or up through the floor to an exit point at least 3 metres away from the building's foundation — directing water toward a drain, street, or garden area that can absorb the flow without causing a nuisance.
- 4
Connect the power supply
This step must involve a licensed electrician. The pump needs a dedicated earthed socket, and best practice in damp below-grade environments is an RCD-protected circuit. If you are adding a battery backup pump — strongly recommended for properties in areas prone to storm-related power outages — the backup unit connects to its own sealed lead-acid or lithium battery and monitors the primary pump. The electrician should test the circuit for proper earth continuity before the pump is run.
- 5
Test the system and set a maintenance schedule
Once everything is connected, pour a bucket of water into the basin and watch the float rise and trigger the pump. The water should be ejected within seconds and the pump should switch off cleanly as the level drops. Check every joint on the discharge line for leaks. After sign-off, test the system every three to four months by pouring water into the pit, and clean the basin of silt once a year. Replace the pump every 7–10 years or sooner if output drops — and test your battery backup annually by unplugging the primary pump.
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FAQ
- Can I install a sump pump myself without a plumber?
- The mechanical parts — setting the basin, placing the pump, and fitting the discharge pipe — are within reach of a confident DIYer who has cut concrete before. However, the electrical connection to a dedicated socket must be done by a licensed electrician under Greek wiring regulations, and any cutting of structural concrete floors should first be checked against the building's structural drawings. For rental properties and hotels, professional installation also provides a documented paper trail for insurance purposes.
- What size sump pump do I need for a typical Greek basement?
- Most residential basements in Greece are well served by a pump rated at 0.25–0.5 horsepower (roughly 190–375 watts) with a flow rate of 30–60 litres per minute. If your basement is large (over 100 m²), sits in an area with a high water table, or has experienced rapid flooding in the past, size up to 0.75 HP and add a backup pump. Your plumber can calculate the required flow rate based on the basin size and the elevation of the discharge point.
- How do I stop the sump pump from running constantly?
- Continuous running usually means the float switch is set too low, the check valve has failed and water is cycling back into the pit, or there is an active groundwater leak entering faster than the pump can handle. Check and re-position the float first. If the check valve is at fault, it is an inexpensive part to replace. If the inflow simply exceeds the pump's capacity, you may need a higher-rated unit or an additional French drain system around the perimeter of the basement to reduce the volume reaching the pit.