How To Choose Your Ideal Sewage Treatment System

The 10 things you should consider before parting with any money.

questionThere are so many things that need to be considered when purchasing a waste water treatment system here in France so how can make sure that you’re choosing the best one for you?

This is a guide to some of the things that you should consider before making any purchase and to ensure that you end up with a system that’s suitable for your property, meets all your requirements and is legal for use in France.

Ten considerations that should ensure you get the ideal system for you.

1) Usage
gdfThe type of system permitted differs between a home lived in all year round and a secondary or holiday home occupied intermittently throughout the year as SPANC (the governing body in France for domestic waste water systems) have deemed that any system that requires an electrical input to function should not be installed in a property that is not a permanent residence. Translated, this means that holiday homes, second homes and gites etc cannot have a microstation as a sewage treatment system as these systems tend to use electricity to run compressors to assist in the purification process. Instead, these homes will need to install some type of filtration system like a fosse and filter bed or a compact filter system.

2) System size
You second major consideration is the size of the system you’ll need and, surprisingly, this is not related to the number of people living in the house or the number of bathrooms the house has. Instead the size of the system required is directly related to the number of principal rooms (pièces principales) the property has or will have. So, what is a principal room? Well, there doesn’t seem to be an exact definition but it’s basically any room that is used or can be used as sleeping quarters or rooms of rest. As such, service rooms such as kitchens, bathrooms and laundry rooms are not included as principal rooms but living rooms, offices and play rooms may be included so long as they have a minimum height of 2.30m, a minimum surface area of 7m² and have an opening onto the outside. Simples! *1

So, having gone round and counted your principal rooms how does this help you work out what size system you need? Well, for every principal room there is assumed to be a principal person who, during the average day, creates a set volume of waste water and emits a set volume of impurites (if you know what I mean!). In France that principal person is known as an equivalent habitant or EH. So 1 principal room = 1 principal person = 1 equivalent habitant = 1EH. All systems on the market are given an EH value and so as long as you know how many principal rooms you have, you’ll know what size system you need and you just choose a system with that EH value. However, there is a minimum size of 4EH, so a house with 1-4 principal rooms will need a 4EH system, a house with 5 principal rooms a 5EH system and so on.

3) Cost and Finance
moneyNow you know what you want and how big it needs to be you need to consider cost. There are two initial costs you need to look at, purchase cost and installation cost.

The purchase cost of systems vary enormously although as competition between companies increases the systems are becoming more affordable. So when looking at systems beware of your budget and shop around. Make sure you have a list of all the things you want from your system and research different systems comparing the specification of each as you go.

The installation price is something you need to negotiate with your installer. There are several materials that you will need to purchase and your installer should know the best places to buy them from. You will also need digging equipment so hire costs are a consideration. Make sure you get a breakdown of costs from your installer so you know exactly what you’re paying for.

4)Ground conditions
The geology and structure of the ground in which the sewage treatment system is to be sited may also have an impact. Specific factors to consider are

  • presence of a water table – a high water table may mean the system needs to be anchored and some systems are easier to anchor than others
  • the presence of underlying rock – longer shallower systems may be more suited to areas with bedrock to save on the amount of digging required
  • size of plot – smaller, deeper systems may be more suited to properties with very little land space availalble.

5) Maintenance
maintenanceThe amount and cost of system maintenance also needs to be considered as, to ensure the continuing effectiveness of the systems they should be inspected on a regular basis. Each system will have it’s own maintenance guidelines so look closely at this noting which parts may need to be replaced and how expensive these parts are. One of the costlier parts of maintaining a system is the de-sludging or emptying of the tank so be aware of how often it is anticipated this will need to be done.

6) Ease of installation and level of disruption
Installing a sewage treatment system is obviously going to cause some disruption and create a certain level of mess. However some systems are easier to install that others so talk through the anticipated level of disruption the installation is likely to cause.

7) Position of the system
In all systems gravity plays a role in one way or another so if you have very little slope to your land then choose a system with changeable invert levels which can then be placed at various depths and if you have a steep slope to your land then you may wish to consider a compact filter system which discharges from the bottom so may involve less “making good” at the end of the installation.

8) System Negatives
Most systems produce some odour or some noise and, if due to the terrain, the system needs to be sited somewhere where this could affect your enjoyment of your land and garden then choose systems with reduced noise or odour levels. Additionally, if something goes wrong with your system there will be some type of alarm that lets you know. If your system is to be placed somewhere where the alarm is visible you may want to consider a system with an illuminating alarm however, if the alarm is not on general view you should consider a system which has an audible alarm.

9) System Legality
spancThe system you install needs to have been approved for use in France and given an agreement number. Any system that does not have this agreement number will be considered as non comforming and will need to be replaced. Ask you supplier for this number and a copy of the “avis relatif aux l’agréments” to ensure that the system is on the list of approved systems. Beware of purchasing cheaper systems from the UK. Most of the British systems now approved for use in France have been modified in some way before being granted an agreement number so although a system purchased in the UK may look the same and have the same name, they may not be legal for use in France.

10) Warranties
All systems come with some sort of warranty so check these out as the length of the warranty tends to vary considerably between the systems

You should now have a really good idea of the type of system you want and the things you should consider when purchasing a waste water treatment system. Any reputable supplier should be able to discuss all elements of the systems they supply so don’t be afraid to ask. Purchasing and installing a new sewage treatment system is both costly and disruptive so to make sure you get it right first time, do your research and find a supplier that is willing to discuss each and every aspect with you.

Whichever system you choose some words of warning.
Firstly, before buying any system, always make sure that you get initial approval for the installation of your favoured system. This will usually be from your local SPANC office the details of which can be obtained form your local Mairie.
Secondly, always buy your system from a reputable supplier and make sure that the system you buy is one that is approved for use in France. The list of approved systems can be found on the SPANC website.

And finally, when installing your system use a reputable installer as in most cases the the efficiency of the system relies on the correct installation and commissioning of the system. Most system suppliers will only guarantee their products if they are installed by an approved installer so be careful who you choose as it could potentially cost you more money and hassle in the long run. And that is the subject of our next article. Entitled “How To Find The Best Installer” this article will look at the questions you should ask and the information you should obtain to be sure you find an installer capable of doing the job.

*1Information taken from
articles R 111-1-1 et R 111-10 of the “Code de la construction et de l’habitation”
“Décret n°2005-69 du 31 janvier 2005 relatif aux avances remboursables sans intérêt pour l’acquisition ou la construction de logements en accession à la propriété et modifiant le code de la construction et de l’habitation” sections 2.1 & 2.2