The simple answer to this is: not in all cases. If you simply flush a full cistern of water into a toilet that appears to be blocked it could easily overflow. What you’re doing here is taking the risk that the weight of water in the toilet bowl will be enough to clear the blockage. Which, unfortunately, it often isn’t if the blockage is quite solidly built up.
To most people, the prospect of trying to clear a blocked toilet is not a pleasant one. Even if you have a plunger and a pair of rubber gloves at hand, it assumes the blockage is within the trap rather than further down the pipework or in the soil stack. Frequently, this is not the case, but our team of specialist drainage engineers can clear blockages from these sites.
If you use an at-home method such as washing up liquid to lubricate the system and loosen the blockage, take care when you flush the toilet to check if the water drains away as normal – be prepared in case it doesn’t.