|
While the occasional smell of drains, can help remind us we are lucky enough to be living abroad, the average Brit certainly won’t accept such smells emanating from their own bathroom, drain smells are however a common problem in many homes including new ones.
Drain smells, depending on the cause can sometimes be very easily remedied, or involve more costly and disruptive works. Diagnosis of the problem is therefore important before any remedial expenditure occurs.
The good news is, that the most common cause of drain smells is due to one or more of the water traps simply evaporating 1. Due to the hot climate and 2. When certain appliances or bathrooms are seldom used. In such cases, all that’s needed is a 10 second run of the tap and a flush of the WC in the offending bathroom. If you don’t use the guest bathroom for months on end, you will probably need to quickly fill the traps every couple of weeks in hot weather. Don’t forget the bidet, which is often the first appliance to offend, as it may not be used even when other appliances are. Always try this solution first, before even bothering to start looking at the drainage system itself.
If trap filling does not work and the smell remains, or quickly returns (e.g. within a week), Check that none of the traps are leaking, smell each appliance (or get a guest who has overstayed their welcome to do it), and if one smells while others don’t, fill the trap and have a good look/feel around it to see if it is leaking. Generally re-seating of the rubber ‘o’ ring, purchase of a new seal or adding some silicone or Teflon tape may suffice, or if access is easy, simply replace the whole trap. (If all appliances smell, they either all leak or it’s more likely that strong siphonage is occurring).
If trap sealing fails to eliminate the smell, it may be that some downpipes, (those than run vertical) are simply sitting into the main pipe with no seal (common in some older properties). Sealing the gap with silicone will usually suffice. The base of the toilet may also need sealing to the floor,(vertical WC integral connections, may include a rubber gasket but pipes commonly just sit in the unsealed waste pipe). Run a piece of paper around the edge and if you can slide it between the WC base and tiles, (including at the rear) there is no seal, use an acrylic bathroom sealant or waterproof grout (leaves a cleaner finish than silicone) to stop the gap.
If after carrying out the above, the smell remains, the problem and solution is going to involve more extensive works.
In addition to the above common causes of drain smells, the water traps from appliances can be siphoned out for a number of reasons, or, backpressure can occur:-
Siphonage causes:-- Due to lack of vent pipes, full bore flow of the drains (e.g. when two WC’s are flushed at the same time), sucks traps from the appliances, which are connected to the same unvented drain. (Some WC’s in back to back properties may discharge to the same main soil pipe, such that your neighbour’s loo could be sucking your traps out. Otherwise it may be your one of your loos sucking the trap of the other out, depending on how the main soil pipe is connected). All UK installations normally feature a ‘stack’ vent pipe (even if it just a ‘stub stack’ with one way valve). Nearly all Spanish houses don’t include any venting.
- The pipe run from one or more appliances is too steep or too long, such that the water flowing away sucks some of the trap out too. (This is rare on flat bottomed appliances, as ‘trailing’ water e.g. in the bath or shower, helps to refill the trap. Round bottomed basins and bidets will be more prone!
- Simple ‘S’ traps can also be more prone than bottle or ‘P’ traps.
- Some pipes may be of undersized bore, such that they flow at full bore. Sinks baths and showers should be 40mm while only the wash hand basin can reduce as low as 32mm. (some older Spanish lead pipework is of very small bore).
Back pressure causes:-- Occasionally when a large discharge of waste meets a tight bend, backpressure can cause the foul air to be pushed back through the water trap.
- If the distance between a discharge pipe from an appliance and the base of a stack or another tight bend, is less than 450mm, back pressure can also occur.
- A non-vented cesspool can also result in a build up of gases, the pressure offer which may push foul air through a trap. Multiple properties (e.g. quads) discharging to the same tank may also suffer more problems. Septic tanks can also cause this problem if they become water logged, or the soakaway function is poor. A supply of oxygen is also needed to help anaerobic breakdown of waste.
While back pressure might be alleviated by venting and softening tight bends, siphonage can only be prevented by providing sufficient venting to individual appliances or at least to the main waste pipe, via a discrete ‘stub stack’ (which normally sits in the corner near the WC) or full stack which can be run externally or internally and either finish above the highest window or terminate in a ventilated roof void via a one way valve.
Changes to pipework and installation of vented stacks, will normally call for tile removal, excavation, breaking of some walls /floors and other significant disruption to the building fabric. Ideally such measures should have been taken at the time of build, but this is simply not standard practice in Spain. It may be possible to alleviate the problem by adding a vent to the waste pipe outside the building, the good news is, smaller valves including an all in one trap/valve (‘Combi-siphon’), can be used to eliminate the need for larger venting systems. ‘Studor’ make a number of such ‘Air Admittance Valves’ (AAV’s),‘Valvulas De Ventilacion’ in Spanish. which are distributed in Spain by ‘Aquatecnic’, (more info via www.aquatecnic.com) , even if your plumber is not used to installing such systems, replacing bidet and basin traps with vented traps, should be relatively self-explanatory for them to carry out. If your plumber refuses to acknowledge the need for ventilation, find a different one, (a good plumber should at least have knowledge of the requirement and solutions. More serious siphonage to the WC itself will require a bigger stub stack valve. But before you panic about poor seals, AAV’s, stub stacks and expenditure, go and run some water in those traps and the problem might just be solved.
NB:- Information for advice purposes only. Proper legal procedures should be followed for all property purchases.
Information provided by Mark Paddon BSc Hons Building Surveying. ICIOB. Property purchase advisor in the Valencia region. www.surveysspain.com T: 962807247
M: 653733066 for free e-mail advice send questions to
This email address is being protected from spam bots, you need Javascript enabled to view it
ã Mark Paddon 2006
|
Home Maintenance 
