Demand call for secondary drain line draining from a gas system. Upon arrival customer showed the attic access and we figured out that the primary drain line terminates in the kids restroom and that both units tie in together. Customer also stated that her daughter had clogged that sink up before with tissues but had been addressed and the sink was draining properly. During my inspection I found the drain pan to have a lot of water and to be rusted which is starting to show its ugly face on the bottom of the drain pan. I confirmed a clogged drain and had a conversation with the customer about what options she had. She decided to just flush the drain line out and leave the drain pan as is for now. After flushing the drain line and treating it with total C the systems are draining properly. I informed the customer that this type of work doesn’t have any kind of warranty and it can get clogged up again. Customer understands and will help us out by pouring white vinegar or bleach down