Smell in grey tank

[Rooksfive]

I am having a rotten.egg smell come from my kitchen grey tank. I have heard of a product called Roebic K 67 and they say it is to clean out drains in your brick and stick drain. Has anyone used this produc or do you have a product you have used in the past. thanks

[Tall-Pines]

I found a document that might help?
It is called Wastewater Geo Method ... a natural method and good tips to handle RV waste water.
I copied it to my website and you can find it there using the hyperlink above.