In some circumstances it may be a soil stack vent, rather than the vent from a waste treatment system, that is the source of unwanted odours.
The purpose of the soil stack vent is to neutralise the negative pressure waves, that are created by the discharge of appliances, by allowing air into the system. However, since it also provides an open airway to the contents of the sewage system it can also give rise to odour problems when badly sited.
In theory, our filters can block the unwanted odours and may appear to be the ideal solution. However, the limited airflow capacity of the filters could lead to other problems such as the siphoning of traps in appliances such as shower trays and handbasins.
If you think your problem is being caused by a soil stack vent, you should be installing an Air Admittance Valve (AAV) rather than a two-way odour filter.
N.B. Before you install an AAV on to the soil stack vent, you must ensure that the sewage system is independently ventilated, or that there is a second open soil vent. Failure to do so will cause a dangerous build up of sewer gas within the pipework.
Air admittance valves (AAVs) are pressure-activated, one-way mechanical vents, used in a plumbing system to eliminate the need for conventional pipe venting and roof penetrations.
A discharge of wastewater causes the AAV to open, releasing the vacuum and allowing air to enter the plumbing vent pipe for proper drainage. Otherwise, the valve remains closed, preventing the escape of sewer gas and maintaining the trap seals.
Using AAVs can significantly reduce the amount of venting materials needed in a plumbing system, allow greater flexibility in the layout of plumbing fixtures, and reduce long-term roof maintenance problems associated with conventional vent stack roofing penetrations.
Whilst AAVs have been around for many years their use until now has been limited to internal installation by local planning regulations. However, improvements in technology, together with a new European standard for AAVs (EN12380), have resulted in the availability of valves that have been fully approved for external installation.
The FloPlast AX110 has been designed for push-fit installation directly into 110mm UK designated pipe, with the use of an EDPM finned seal.
Push-Fit connection means that it can be easily removed, as necessary, to provide a secondary rodding point.
Designed for use on discharge stacks up to 45 metres or 10 storeys high.
Airflow capacity = 43 litres/sec.
The AX110 must be installed in a vertical position a minimum of 200mm above the highest branch connection.
The BS EN 12380 A1 rating of the valve means that it can be located below the flood level of the appliances being vented.
NB. The AX110 should not be used when the discharge stack to which it is fitted provides the only ventilation to a septic tank or cesspool.