spill over or carry over?

English as a Second Language English Vocabulary, Grammar and Idioms
1

Dear ALL,

we have a vessel which contains sand, this vesel uses for filtration water. sometime it will back wask (back flow to clean sand/vessel). when back wash, there is some of sand is comming out from bottom to top and go to outside. how can i say this case: “sand carry over with water flow” or “sand spill over with water flow”?
or others sentence.

please advice me.

thanks.

2

When the vessel’s backwash stage is automatically actioned, some of the filtration sand is entrained within the water and escapes through the overflow line.