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A very important aspect during the use of a shower tray siphon is the relationship between the height of the siphon body and the height of the water seal (the column of water in the siphon).
It is the most effective protection against hydrogen sulfide odors from the sewage system.
According to the EN 274 standard, the minimum water seal height in a siphon is 50 mm—this ensures effective protection against unpleasant odors in a regularly used bathroom. In extreme conditions, such as negative pressure and underfloor heating, a 50 mm water seal will evaporate only after about 2 weeks, and under typical conditions even after 6–8 weeks.
But how can you achieve a 50 mm water seal if the entire siphon body is also only 50 mm high—as expected by today’s plumbing market?
There are only two possible solutions:
- Reduce the water seal height to a reasonable level, e.g. 40 mm—still an acceptable compromise, providing a high level of protection in practice (only about 20% less effective than the standard). This solution is used in low-profile shower siphons from Akces, Speed 2 series.
- Use a mechanical seal—such as a silicone membrane or a secondary trap located elsewhere. However, this is very rarely applied in residential construction.
Risks and trade-offs
- Silicone membrane – although modern, it may become damaged or blocked, especially by debris. It can be replaced, but not without cost.
- Too low water seal (e.g. 20–30 mm) – often found in low-cost siphons; unacceptable unless combined with an additional odor-blocking mechanism, as evaporation may occur within a few days.
- Direct connection without a water seal – sometimes seen in temporary installations (e.g. low-cost campsites or in developing regions), but not suitable for proper sanitary use.
It is worth noting that the EN 274 standard was developed over 30 years ago and does not account for alternative sealing methods other than hydraulic ones, such as flaps or membranes.
In the case of choosing a Speed siphon, no compromise between installation height and water seal is required. The Speed body, with a total height of 72.5 mm including the gasket, accommodates a full 50 mm water seal, ensuring 100% compliance with the EN 274 standard in this parameter.
