So, the WRAS adjustment isn’t a limitation, but a gentle reminder that approvals and temperature ratings must be checked together. Other Relevant Approvals: BS 6920 / KIWA / NSF. WRAS is not the only certification to review or consider when choosing jointing compounds:
Approval What it Confirms Why it Matters BS 6920
Product is chemically safe when in contact with drinking water
KIWA
Meets strict European water safety and stability standards
NSF
International potable water safety certification
Protects taste, odour, colour, and water chemistry
Essential for global and high- specification projects
Recognised globally across commercial sectors
Products supported by several certifications have the potential
to provide stronger assurance of long-term safety, especially where uncompromised water quality in high-risk areas is paramount. The hidden issue: Overusing jointing compounds Jointing compounds can work well when applied correctly, but overuse/application can be a common and costly mistake, which can lead to serious water quality problems. What goes wrong when too much compound is applied:
• It has the potential to be pushed into the pipework during tightening
• The excess travels through the system • It can accumulate in valves, strainers, aerators, or filters • Where the compound is captured, it can provide an area for biofilm formation which can lead to microbial growth contamination • Restriction in flow where the compound has settled in valves, strainers, aerators, or filters. In severe cases, this can: • Reduce operational performance o Cause valve malfunctions o Increase maintenance for cleaning
• Compromise overall water quality, leading to adverse microbiological sample results.
Best practice application (if required as a last resort) A safe and hygienic installation requires: • A thin, even application only on male threads • Avoiding smearing compound into fittings or pipes • Post-installation flushing (with no restrictions i.e., filters, strainers in place) to clear any residue
• Selecting only the amount of compound that required to complete the task. If compound squeezes out when tightening a fitting it is evident that too much compound has been used.
Why some subject matter experts recommend reducing or avoiding use Due to the potential water quality concerns, it has become apparent in project specifications that the use of jointing compounds is to be avoided wherever possible, especially in water systems containing: • Thermostatic Mixing Valves/Taps (TMVs/TMTs) • Fine strainers (e.g., inline Y-strainers) • Tap filters / aerators. Alternatives include, but not limited to: • PTFE (Teflon) tape or cord • Pre-formed sealing washers (Non EDPM). The above options create an effective seal without introducing
excessive debris into the domestic water systems, with the below results: • Reduced risk of bacterial growth • Longer system lifespan • Simplified compliance • Lower maintenance and callouts Summary Jointing compounds may remain an important part of plumbing practice, but their use must be smarter and better informed than previously. The WRAS test temperature change from 85°C to 23°C does not prohibit hot water use; instead, it emphasises the responsibility of installers to verify suitability and prioritise system hygiene.
By ensuring the correct product choice, using minimal quantities, and exploring safer alternatives where appropriate, we can protect both the water system performance and public health, along with the safety of the end user from any potential infection issues.
JW250
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