This pressure washer attachment is amazing!
I own a domestic Karcher k3 and used this "Sludge Sucker" to clean out my 2x Rain Water Tanks and large outdoor fish pond.
The fishpond used to take 2 days with a garden-hose sucker attachment, this gadget did the same job in 2 hours!!
My 15 year old poly rainwater tanks have never been cleaned, and they were gross, it took just half a day to bring them back to brand new.
Needless to say that I recommend this however it is worth going to your local hardware store to get some longer drainage hose to pump the sludge further away.
However, be aware that the "pumping head-height" of this attachment will be determined by the power of your pressure cleaner. My k3 struggled to pump the 2.4m head-height out of the tank inspection hatch, although with some syphoning and pumping the attacment up and down, I was able to get it to work, but I don't doubt that a more capable pressure cleaner would not find this to be a problem.
I'm very pleased with this purchase, I highly recommend it, and I have shown it to quite a few people.