If your drains are clogged and backed up you may have a bigger problem than you can solve on your own. Many bathroom clogs are caused by hair going down the shower drain while kitchen clogs are generally caused by grease being poured down the drain and becoming a solid clog. If commercial chemical products do not clear the blockage you may have to consider the need to have a professional plumber come in and clean out the drains.
Homes with older pipes are sooner to becoming clogged than years of accumulated gunk, hair and grease and an endless list of other things that have gone down the drain over the past few decades to have finally built up and settled into an unmovable mass that is causing Your pipes to drain slowly if at all.
Another possibility is tree roots have started to penetrate the sewage and water lines causing a blockage. This can be possible even if the nearest tree is not on your property unfortunately. Trees can have long and deep roots that grow into whatever may be blocking their path including sewage lines.
A lot of people hope if they just leave the clog alone it will right itself but a clogged drain left unattended can lead to sewage back up in not only the toilet but also the sinks, and bathtubs so this is not an issue to ignoring having it Will resolve itself.
In either case this type of drain cleaning job is something that only a licensed, professional plumber should tackle because of the potential to do more harm to your system if done incorrectly. A plumber will use an electric snake to penetrate and sweep out everything that is in its wake in the lines and if this is done by a novice the results can be broken pipes and leakage.
A plumber will likely use an electric snake to clear the blockage in the drains. This type of snake is very fast- it can spin five hundred reps per minute and has a feed of two hundred feet. Due to the high rate of speed that this snake operates at it needs to be used by someone who knows how to handle it effectively such as a plumber.
For inside drains a plumber will likely use a smaller snake to clean out sediment and pipe blockage to resolve a smaller drain clog problem. Once your drains are cleaned out make sure to take preventive measure such as cleaning hair out of drains and not pouring grease down the drains and hopefully your drains will be clog free for a long time to come.