I N S T R U C T I O N S​



for installation of polyethylene tanks – LLDPE 

The tanks are made of polyethylene with a wall thickness of 8 to 12 mm. and are intended for storage of water and liquids that are not aggressive to polyethylene, as well as drinking water. The tanks are not designed to be exposed to positive or negative pressure.


The excavation should be 50 cm to 70 cm larger than the size of the tank. The bottom of the trench should be compacted (tamped), leveled and lined with 20 cm of sand or felt with a grain size of 5 – 15 mm.

1.1. The tank should be carefully unloaded manually or through construction mechanical equipment, using a metal rail for tanks above 20,000 litres. In the same way, the tank should be carefully laid in the trench and should be well leveled in all directions.

1.2. At least 2/3 of the tank (preferably the whole) must be buried with felt  – river ballast (6 to 30 mm fraction) and compacted / tamped / well. To equalize the external and internal pressure after 1/4 of the equipment has been buried it must be filled with liquid (water) to the same level and then tamped with a hand rammer (vibrating rammer or frog rammer). In this way, the tank is buried, compacted and filled in 4 stages. If the inert material around the tank is not compacted properly, a distortion of the tank may occur. Underground tanks provide shape and tightness, and the materials around them in which they are buried as well as the quality of the installation ensure the stability of the entire equipment. Tanks cannot be treated as a supporting structure.

1.3. The soil above the tank should not exceed 0.50 m, because due to its important weight it can deform the equipment.


  1. GROUNDWATER: In case of risk of high levels of groundwater or drainage and rainwater, a concrete slab must be built to which the equipment must be fixes through metal rails / ropes. In some cases, 1/2 of the tank height may need to be filled around with concrete and then to continue to make the embankment with the type of aggregate described in item 1.2.

1.2. CLAY TERRAIN: When installing the equipment in clay soil, it is necessary to build a drainage system that drains the groundwater. Otherwise, this water can cause additional tension on the tank and even cause it to bend. 

1.3. SLOPING TERRAIN: When burying the device in highly sloping terrains with a probability of moving earth masses, it is necessary to build a concrete wall that prevents possible soil pressure on the device. 

1.4. BURIAL IN A PARKING LOT OR IN A STREET: The area above the tank can be used for green spaces or pedestrian zones. It is not advisable to build a parking lot or car passage on the equipment. But if this is necessary or if the equipment is to be buried to a depth of more than 0.50 m, it is necessary to build a precisely calculated protective reinforced concrete slab that steps on non-digged soil and from there to distribute the pressure exerted by the earth masses and the vehicles. The weight of the reinforced concrete slab must not be carried by the equipment (the tank). If deep burial of the tank is necessary, it is required to extend the inspection shafts, which can be done with the help of a polyethylene shaft with a diameter of at least 800 mm.

1.5. OTHER FEATURES: Pipes of different diameter (max. Ø 250) can be connected to the equipment by means of a rubber sleeve or by welding. The tanks can be connected to each other through pipes, thus increasing the total volume. 

1.6. In all circumstances, the following must be clarified before the installation begins. 

– Soil structure.

– Maximum groundwater levels that occur and soil drainage capacity.

– Types of load.


M&J Bulgaria EOOD guarantees the perfect operation of the tank only in case of strict observance of everything described in the “Instructions for installation”. 

Guarantee periods:

Tank guarantee 60 months.

Mechanical parts guarantee 18 months.

Material guarantee 25 years, subject to the same instructions.

The guarantee begins from the date of purchase.

The guarantee does not apply:

In case of non-compliance with the above instructions or careless handling of the product.

In case of incorrect assessment of the terrain.

In case of mechanical damage by the client or a third party.

In case of damage due to natural disasters – floods, fires, earthquakes or other force majeure.

The client may invoke the rights arising from the guarantee only within the specified guarantee periods, by giving written notice to the trader or the manufacturer.

I am familiar with the instructions for installation: three names / signature of the client or an authorized person /. …………………………………………………………………………………………………………………………………………..

  • hree names (of the client or an authorized person)  – signature

Date: ……………………….                                   Seal and signature of the seller: ………………..