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Frequently Asked Questions

Why should we choose WAM UK?

WAM UK has over thirty years experience in sewage treatment plant design, management and pollution control. Our clients range from individual properties to large commercial organisations . Such is the quality of our design and installation work that we are a fully certified installers for all major packed treatment suppliers in the UK, and have been for many for a number of years.

What type of domestic drainage system do I need?

If you require a domestic drainage scheme you can use our Site Assessment and System Selection Questionnaire to help you select the best solution for you site.

Whatever system you choose, you must satisfy the relevant authorities that it will:

•Treat or contain the effluent, providing a long-term sustainable solution

•Be correctly specified to cope with expected usage levels

•Pose no threat to water resources

• Prevent nuisance

What can I do if I have Septic Tank Smell problems?

If you are having problems with your septic tank please view the Operation of Septic Tanks PDF.

Why not use just a Septic tank or Cesspool?

In the UK, the Environment Agency, SEPA and Local Building Control Departments govern what system you can install to treat your sewage & wastewater. Cesspools & Septic Tanks often do not meet with local regulations as they offer little or no treatment for the pollutant waste.

Treatment Plants

What size treatment plant do I need?

The size of the treatment plant you need is dependant mainly on these factors; the number of residents, the number of properties and the location of the installation. The final model and size will be ascertained once we have this information and have carried out our site visit.

A Treatment Plant from WAM UK still requires approval but is already the preferred option in many areas with local authorities and environmental agencies.

What quality of water is produced?

With sewage treatment, water quality is defined by the level of three forms of pollutants that are present in the water exiting a treatment plant. The three pollutants are


1.BOD - Biological Oxygen Demand (a measure of the biological pollutant load)

2.SS - Suspended Soils (small particles of waste matter)

3.Ammonia - (Ammonia is the chemical that creates urine odour)

The better a treatment plant’s performance, the lower level of these pollutants, expressed in milligrams per litre – WAM UK will only specify treatment plants meeting the strict regulatory guidelines.

It is important to bear in mind that discharged water from any plant is not suitable for consumption or washing but a sample will have a high level of visual clarity.

What power is needed and how much will it cost to run?

All WAM UK Treatment Plants require an electrical supply and are extremely economical to run, often costing less than a 60watt light bulb per day.

For example in 2005, the BA BioDisc gained certification to European Performance Standards, the Testing Engineer’s official report stating a mean power consumption of 1.3kWh/d (roughly 14 – 20 pence per day, depending on supplier).

What would happen in the event of a power cut?

A power cut should not cause any particular problem, but in all events, check that unit has restarted after a power cut of any length of time and reset the control panel if necessary. If the unit fails to restart then please contact us.

What can I put down the drains into my treatment plant?

Please see the How to keep your sewage treatment plant running sweetly PDF.

What is the new European Standard and why is it important?

En12566 Part 3 - The New European Standard for Domestic Sewage Treatment Plants

New European guidelines require manufacturers to submit their plant to a strict uniform testing regime that will accurately measure and compare the performance of treatment plant up with a population of up to 50. These tests identify how much pollution the plant removes from the sewage, what level of maintenance is required, what power is absorbed and therefore give the user a true basis for comparison.

All plants that have undergone this test will carry a CE Mark label, giving buyers reassurance and a clear comparison to help select the best product for their needs.


Do I need to get Planning Permission?

All new Wastewater treatment systems require Building or Planning permission. Adding a secondary treatment system (such as a Reed Bed) may also require building/planning permission. WAM UK would advise to check with your local planning authority.

What permissions are required before installing a tank/plant?

In the UK, any unit going into the ground may require ‘consent to discharge’ from the local Environment Agency / SEPA office, even if you are using just a storage tank. Planning/Building permission is required from the local Building Control department. Please click to view our links to the Regulatory Bodies websites.

Can I connect surface water into the treatment plant?

Unfortunately no surface water can enter a treatment plant and must be drained away separately. An unknown amount of rainfall flushing the bacteria through the system will cause the treatment to deteriorate.

Where can I discharge to?

Every location has its own characteristics and hence there can be either many discharge options, or none at all. Popular options include soakaways, drainage ditches or discharging to streams, rivers & watercourses. Again, it is important to remember that what is judged acceptable to the authorities in one location can be turned down by another, so the first step is always to consult your local Regulatory Body.

What is a percolation test and who carries it out?

Click here.

What can I do if I have a high water-table in my area?

Whether you have a septic tank or a sewage treatment plant installed, an effluent pump station can be used to transport and discharge the effluent to a level higher above the water table. This ensures that you reduce contamination of the ground water, and also means your drainage system will not back up when the water table is at a seasonal high.


WAM UK offer a full commissioning service for all major manufacturers equipment, of which a commissioning certificate will be issued.

Pumping Stations

How many times/day do they switch on/off?

Pumping Stations have sensors to activate the pump when the volume reaches a pre-set level. When the level falls the pump switches off.

Due to the wide range of pump options and variety of applications and conditions, each system will have its own individual number of on/off cycles.

What can I put through the pump station?

Please refer to the pump station Do & Don’ts that come with the particular station.

What are the running costs?

WAM UK selects and installs pumps from leading manufacturers to provide the best performance and power efficiency for each application. Electrical running costs are often very low as units remain dormant for periods between operational cycles.

What maintenance and servicing is involved?

WAM UK package pump stations are designed for minimum low-cost maintenance. We recommend regular servicing inline with the manufacturers’ guidelines which includes the chamber, the pumps and all of the controls. We can provide a full after-sales service and maintenance contract if required.


What type of Separator do I need?

To determine what the correct separator for your needs, please follow the link to the separator section.

What is the difference between Full Retention and Bypass units?

Full Retention Separators treat the full flow that can be delivered by the drainage system, (normally equivalent to a flow generated by a rainfall intensity of 50mm/hr). Bypass Separators treat all flows up to 5mm/hr. This covers up to 99% of all rainfall events. Flows above this rate are allowed to bypass the separator.

Where can they be discharged to?

Separators (by design) fall into two categories, depending on where they can discharge to: Class I separators are able to discharge to a surface water drain, or a soakaway. Class II separators must usually discharge to a foul sewer; each subject to environmental regulator - EA / SEPA / NIHS or water authority consent.

Should an alarm be fitted?


Pollution Prevention Guideline number 3 (PPG3) issued by the Environment Agency states;


‘Separators must be provided with a robust device to provide visual and audible warning (if necessary to a remotely located supervisory point) when the level of oil reaches 90 per cent of the oil storage volume (V) under static liquid level conditions. This automatic warning device indicates that the separator is in need of immediate emptying for it to continue to work effectively.’

(Provided by kind permission of the Environment Agency)


What pipework/inverts can we supply?


Please consult our product data sheets or download our Pipework Orientation PDF.


What maintenance is involved?


Periodic desludging is required approximately every 6 months, depending on usage.

An oil level alarm system can be purchased as required by the Environment Agency which gives an alarm indication when the separator is at 90% of its capacity, thereby giving opportunity to arrange desludging before the total capacity is reached.


WAM UK strongly recommends that (at minimum) a manual 6-monthly check should also be part of a maintenance schedule.

How do I vent the unit?

Each Separator has a vent exit pipe mounted in the neck of the tank itself. This pipe will require extending out to an appropriate above-ground atmospheric venting point, but this secondary equipment is not supplied with the Separator unit.

Venting arrangements must meet local requirements and comply with HS(G)41 for filling stations or British Standard Code of Practice BS8301 for other applications.