Previous owner never used screens in shower and sink drains. Consequently, there is a lot of hair in drains. I picked out what I could reach with needle tweezers. Is there a safe chemical to dissolve hair in the trap and holding tank?
Let me start off by telling you not to use any caustic drain cleaners that contain Sodium Hydroxide, Sulfuric Acid or Hydrochloric Acid. These caustic drain cleaners can damage your RV's Plumbing, Holding Tanks, Dump Valves, etc. Also, depending on where your RV is located, it may be illegal to dump your tanks containing these chemicals, as they are harmful to the environment and can be harmful to both humans and pets if they spill while you are dumping your RV's holding tanks.
if you want to use a drain cleaner you should use an earth-friendly drain cleaner such as those that use enzymes to dissolve the clogs. Just remember to thoroughly read and follow the instructions on the drain cleaners you use. Depending on how clogged the drains are, you may have to repeat the treatments several times.
In some cases these drain treatments may not fully unclog the drains and you may have to resort to using a plunger on the drains. It is safe to use a plunger on RV sink and shower drains, just don't over do it. You should also use very hot water when using a plunger, because the combination of the hot water and the suction of the plunger may just be enough to break up a stubborn clog.
Since you are saying that the clogs in your RV's drains consist mainly of hair, you may also want to try a Hair Clog Tool like the one pictured at the top of this page to remove the clog. These tools have little hooks and loops on them that will snag the hair clogs and allow you to pull them out of the drain.
If you have some sinks in your RV that remain clogged after you have done everything above, you can remove the P-Trap (elbow pipe under sink) and use a garden hose or compressed air to clean it out. Obviously this will not work on the shower unless you can access the pipes underneath it.
In most cases the shower drain is probably going to be the most stubborn drain to get cleared up. If all else fails, you might want to take a look at the video below to see how you can get the shower drain unclogged. Even though this video is for a home shower and not an RV shower. the methods shown will work on a RV shower.
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