When I clean our Rienza post trip I put a bowl of hot water with a dish washer tablet devolved in it down the kitchen sink drain.
I havnt had the other drains block or run slow because they are almost direct into the grey tank. The kitchen waste pipe has a loop in it to avoid the prop shaft and chassis. Not an ideal layout but it it mostly works if it’s cleaned regularly.
Hi Sue, by all means try the tabs to unblock any deposits, but all of my motorhomes have had poor draining at some time. It is due to the small diameter pipes and as boris7 said, just plunger it or use the plug as a plunger.
Prevention is better than cure! Use a strainer in the plug hole to stop bits going down; wipe anything greasy with kitchen roll dipped in washing up water before washing. I use soda crystals dissolved in hot water poured down the all the plug holes to clean.
As Potty says...... and in my case I use Aldi's finest washing machine cleaning fluid. 1/2 bottle down the plug holes after each trip followed 30 mins later by a gallon of warm water. Leave in the tank till your next run out.