I never liked powdered Tide because it would fail to dissolve unless you filled the washer, added it, agitated it for 30 seconds, then added the clothes. I wanted to dump in the detergent, clothes, start the water and move on to the next task...
Brilliant me decided to take a gallon jar, add a couple of cups of detergent, fill with water and have a liquid the next time I did the laundry. The result? It gels. REALLY. It turns into "Tide Snot". Far more durable than Jello. It can dry out completely then re-form if you add water. It might live forever in your black tank!
Use Dawn. Use it once in a while... especially if you're going to store the unit or have an open house and show it off. Use it, shake it, drain it, then rinse it thoroughly. It dissolves grease really well and works excellently in the gray tank also.
Today is a gift, that's why they call it the present.