A blocked toilet or backflow, as it is often known, causes serious issues in the property. There are two main causes of blocked toilets:Back pressureBack siphonageWhen you want to know how to unblock a blocked toilet Catford, no matter what caused the blockage, you will need to be awareof several devices that can help you in the process. Air gaps to avoid backflow:This is a simple backflow prevention device. It has an air gap between the water supply outlet and the maximum potential water level in the appliance. It is mostly seen with taps on wash hand basins and sinks. Because of the gap, the contaminated water is prevented from being drawn back into the supply. Check valves to avoid backflow:Regarding how to unblock a toilet, if it is not possible to achieve an air gap,using a single or double check valve instead may be possible. It is associated with a higher risk level. Fitting an outside tap is one of the common DIY tasks. It is considered as a level 3 risk and preventing the backflow from the outside tap may be achieved through fitting a double check valve before the hose union bib tap. Supply to a water softener might be another example. Here the potential risk is gauged to be a level 2, so a single check valve can be used. Situations when check valves do not work:However, the strategy of valve checking is not applicable in all situations of how to unblock a toilet. Check valves do not work in case the fluid risk is more than a level 3. For example, to prevent a backflow at a kitchen sink while using a check valve is not acceptable. Because of the potential contamination here, the fluid risk is level 5. People use the sinks for washing soils from vegetables as well as blood from meat and this can cause a severe health hazard. An air gap device can be useful in a level 5 risk.