Hi @ziucqea,
Thank you for your question and welcome to the Bunnings Workshop community, it is fantastic to have you with us.
It's great to see @jaiprak has already jumped in to assist.
This type of issue commonly occurs due to a problem with the flush valve or the fill valve, which control water flow and sealing within the cistern. Several components are worth inspecting, as any misalignment or minor damage can cause water to escape into the bowl over time.
One of the first areas to check is the flush valve seating. Even with a new seal washer, water can seep through if the flush valve isn't sitting perfectly or is slightly misaligned. Carefully examine the valve for any tiny gaps, debris, or uneven placement that could prevent a tight seal. Sometimes, even a small piece of grit or an improperly seated valve can allow water to pass, causing a persistent leak into the toilet bowl.
The water level in the cistern could also be a factor. If it's set too high, water might overflow into the toilet bowl through the overflow tube. To avoid this, make sure the water level sits just below the top of the overflow tube. You may need to adjust the float or fill valve mechanism to control the water level and ensure it stays below the overflow, preventing the slow trickle of water into the bowl.
Another potential source of the problem is the fill valve itself. A fill valve that doesn’t fully close may allow water to slowly seep back into the cistern, eventually leading to overflow. Check the fill valve for any debris that might obstruct proper closure. If the fill valve continues to let water through after reaching the correct level, it might be necessary to replace this part to ensure complete closure after each fill.
Finally, closely inspect the flush mechanism and any surrounding parts for signs of wear or damage. Concealed cisterns rely on several internal components, such as flappers and seals, to maintain a leak-proof system. Look for cracks or worn areas on plastic or rubber parts that could cause a slow leak. Using food colouring or dye in the cistern can help pinpoint the exact location of the leak if coloured water appears in the bowl. If the leak persists after addressing these points, consider replacing the entire flush valve to achieve a more reliable seal.
If all else fails, contacting a licenced plumber who is aware of your system might be the best option.
Let me know if you have any further questions.
Jacob
