Watertight septic tanks

Q: When is a watertight septic tank required?

It is required on plots without a connection to the sewer network where discharge into the ground is not authorised: areas with a high water table, low-permeability or clay soils, proximity to water catchments, protected natural areas and, in general, wherever the water authority determines.

Q: What material are they made of and how watertight are they?

We manufacture them in glass-fibre reinforced polyester (GRP) and in rotationally moulded high-density polyethylene: lightweight materials that are corrosion-resistant and fully watertight. They include reinforcements to withstand ground pressure, a threaded access cover Ø 620 mm and PVC connections.

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A watertight septic tank is a fully sealed holding tank that collects and stores the wastewater of a home or facility when it cannot be discharged into the ground or connected to the public sewer. Unlike a conventional septic tank, it does not infiltrate or discharge water into the environment: the contents are retained inside until an authorised waste manager empties it.

They are the ideal solution for rural or isolated areas without sewerage, plots with a high water table or sites where regulations do not allow discharge, as well as for portable toilets, site cabins and sensitive locations (water catchments, protected areas). At Inza we manufacture them in glass-fibre reinforced polyester (GRP) and in high-density polyethylene (HDPE), in capacities from 500 to 50,000 litres.

Supply: lead time to be confirmed, depending on size and component stock. Shipping included in the price, excluding unloading equipment at destination; for capacities over 5,000 L, please ask about conditions.

Questions?
Phone: +34 91 127 90 05
WhatsApp: +34 91 127 90 05
Email: info@inzainox.com

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Watertight polyester septic tanks
Price range: €3.000,00 through €15.500,00 taxes not included Select options This product has multiple variants. The options may be chosen on the product page
Watertight polyethylene septic tanks
Price range: €630,00 through €3.750,00 taxes not included Select options This product has multiple variants. The options may be chosen on the product page

Your questions about watertight septic tanks answered

What is the difference between a watertight and a conventional septic tank?

A conventional septic tank carries out pre-treatment (settling and anaerobic digestion) and discharges the water into the ground by infiltration. A watertight septic tank is fully sealed: it does not infiltrate or discharge anything into the environment, but stores the wastewater until it is removed by an authorised manager. It is mandatory where regulations do not allow discharge into the ground.

When is a watertight septic tank required?

It is required on plots without a connection to the sewer network where discharge into the ground is not authorised: areas with a high water table, low-permeability or clay soils, proximity to water catchments, protected natural areas and, in general, wherever the water authority determines.

How often must it be emptied and who does it?

The emptying frequency depends on the tank volume and the number of users. It must always be carried out by an authorised waste manager when the tank reaches maximum capacity. The ventilation pipe should be kept in good order and the level checked periodically; many models accept an optional level indicator.

What material are they made of and how watertight are they?

We manufacture them in glass-fibre reinforced polyester (GRP) and in rotationally moulded high-density polyethylene: lightweight materials that are corrosion-resistant and fully watertight. They include reinforcements to withstand ground pressure, a threaded access cover Ø 620 mm and PVC connections.

How watertight septic tanks work

The wastewater from the home or facility enters through the inlet pipe and accumulates inside the tank, which is fully sealed. As there is no outlet or infiltration, the water remains stored until the equipment reaches its maximum capacity.

When the tank is full, it is emptied through the upper manhole by a tanker truck operated by an authorised waste manager. For correct, safe operation a ventilation pipe must be installed to release the gases generated inside. The models can be fitted with a level indicator and, in the polyester versions, with sludge emptying via a submerged pipe and quick coupling.

Advantages and disadvantages of watertight septic tanks

Advantages

Total independence from the sewer network, ideal for rural or isolated areas.
Maximum environmental protection: being sealed, they do not contaminate the soil or groundwater.
A legal solution where discharge into the ground is not allowed.
Quick, simple installation; compact, lightweight prefabricated units.
Durable, corrosion-resistant materials (GRP and HDPE) with a long service life.

Disadvantages and considerations

They require periodic emptying by an authorised manager, with a recurring maintenance cost.
They do not treat the water: they only store it, so the volume to be removed is the total generated.
The capacity must be correctly sized to the consumption to avoid emptying too often.
They need a ventilation pipe and suitable access for the tanker truck.

Why choose Inza watertight septic tanks?

At Inza we offer watertight septic tanks in glass-fibre reinforced polyester (GRP) and in high-density polyethylene (HDPE), with capacities from 500 to 50,000 litres and vertical and horizontal formats to suit any ground. All units are 100% watertight, with structural reinforcements, a threaded access cover Ø 620 mm and PVC connections.

They meet the technical requirements for autonomous sanitation, with sealing, ventilation and a maintenance record, in line with the applicable water and building regulations and the EN 12566 standard. We advise you on the right model and capacity for your consumption and plot conditions.