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Learning Centre

Plumbing Support

For good practice advice on Hunter Plumbing systems, see our plumbing guide.  You’ll also find information on the complete Plumbing systems here as well.

Do you need help with an above ground drainage design?  Customers who have made a commitment to use or specify Hunter products may benefit from a free design service.

Below is a list of frequently asked questions on the Hunter plumbing range.  If your question is not listed below, please feel free to contact our Technical Services Department on 01622 852695 or email them on technical@hunterplastics.co.uk.

Frequently Asked Soil Question

  1. Check that tight 90 degree bends have not been used instead of swept bends in the soil and vent pipe or at the base of the stack.
  2. Check for blockages in the soil or drain pipes.
  3. Check that the soil stack is connected to a fully ventilated drainage system



Hunter brackets in galvanised steel or plastic are to be spaced at 2.0m vertically and 1.0m horizontally as specified in BS EN 12056-2:2000. Socket brackets are to be used as fixed points around expansion sockets, controlling thermal movement. Pipe brackets which allow for thermal movement, are to be used for lateral support.


A group of ground floor appliances may be connected to the drainage system via a stub stack. A stub stack consists of a short length of 110mm-diameter pipe capped off with an access fitting. Where one or more stub stacks are connected to a drainage system, ventilation must be provided via a soil and vent pipe at the head of the drain. The limiting factors are that the distance from the centre of the pan branch to the drain invert must not exceed 1.5 metres, whilst the highest connection should be within 2.0 metres.


The Building Regulations Approved Document H1, does not allow an Air Admittance Valve to be fitted outside of a building or in a dust laden atmosphere.

Frequently Asked Waste Questions


Trap sizes up to and including 50mm discharging to soil stacks should have a 75mm water seal. However, a water seal of 50mm is allowed on baths and shower trays, also on spray-tap basins provided they are fitted with flush-grated waste without plugs. But traps discharging to a trapped drain gully may have a 38mm water seal. Trap sizes are to comply with BS EN 12056-3:2000


Both systems have their advantages and disadvantages. Check out some of the benefits of the systems below:



  • Cannot be pulled apart 
  • Rigid joints 
  • Relatively easy to assemble 
  • Permanently watertight
  • Can be used externally
  • Does not need protection from daylight 


  • Dearer than the polypropylene system 
  • Lower impact resistance than PP
  • Lower chemical resistance than PP



  • Can be taken apart
  • Flexible joints
  • Offer expansion to longer waste runs 
  • Simple to assemble
  • Less expensive than the solvent weld system
  • Higher impact resistance than muPVC
  • Withstands higher temperatures than muPVC


  • Joints need supporting
  • Cannot be used externally without protection from sun (u.v.)

Frequently Asked Endura Questions


To ensure that the Endura Grease interceptor is sufficient to cope with the appliances being drained, it is important that it is sized correctly. The flow from kitchen appliances passing through the interceptor must not exceed 1.6 litres per second (DSG16) or 3.2 Litres per second (DSG32). A commercial dishwasher may have a discharge capacity greater than the capability of the interceptor. Therefore, you will need information from the dishwasher supplier to convert the water flow through your dishwashers to litres per second. Dividing the total amount of water discharged to the drain by the amount of seconds that it takes will do this.


The outlet pipe from the Interceptor to the drainage system must always be 110mm diameter whilst the inlet pipe from the appliance should be 50mm. Flexible connectors are supplied as standard with every Endura grease interceptor.


The ICD is necessary to regulate the flow of influent (waste water and grease) and introduce air into the system to aid grease separation. The ICD is supplied as part of the Endura installation package and should be installed as close as possible to the sink/dishwasher that it serves. Full installation instructions are supplied with the Endura and provides a guide as to how it should be installed. N.B. Omitting the ICD unit will cause the Endura grease interceptor to be at least 40% less efficient.

The ICD should be installed between the last appliance and the grease interceptor. The Influent Control Device has a cleaning eye that should be checked at the end of the day and any food particles removed.


To work efficiently The Endura Grease Interceptor requires biological additives to break down the grease. Hunter offers the Endura BioPak a programmable automated dosing unit, which injects a measured quantity of Bio-G liquid grease digester into the system at specified intervals. The unit is recommended but not compulsory. However, it is important that some type of degreasing agent is used, as without degreaser the interceptor will build-up with grease solids rapidly, which may result in blocked pipes. The 12.5 litre refill pack of Bio-G will last for approximately three months. Alternatively, BioPlus Granular Grease Digester can be introduced manually.

The Endura BioPlus granular digester must be added daily to be effective, it is introduced manually by pouring a rounded scoop of granules into the sink waste and then flushing this into the Grease interceptor with half a sink of warm water. This should be done at the end of each working day to allow the maximum amount of time for the digestor to take effect within the grease interceptor. A 4x1Kg pack of Bio Plus will last approximately four months and a scoop is supplied with each tub of granules.

Endra BioPlus and BioPak can be ordered through any Hunter Plastics stockist.


Your Endura grease interceptor will need routine periodic cleaning to remove any accumulated grease and food particles. Continuous and regular use of a grease digestor will significantly reduce the frequency of grease separator maintenance. When the unit requires cleaning, the lid should be removed and the grease scooped out and bagged-up ready for disposal by the local authority.

Unlike other Grease interceptors, Endura contains fully removable baffles which can be removed to aid deep-cleaning. Scoop-out the trapped water and clean the unit and baffles with a solution of hot soapy water. Replace the baffles and replenish the trap with water, the lid should then can be screwed back into position.

Hunter recommends that a regular planned maintenance schedule be instigated to ensure that the interceptor continues to operate efficiently.

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