EtG follows an elimination curve very similar to the primary analyte, ethanol. That is EtG elimination is
probably rate limited. Most of the EtG, 90% +,is eliminated during the first 12 hours after peaking (1). Under all theories of elimination there is a ratio between the metabolite in blood and in urine, i.e. blood content is higher during absorption and then that ratio reverses during the elimination phase with urine content steadily increasing while blood content decreases. Not so with EtG(?) Urine EtG is always higher than blood (2)... Even at peak.
What that indicates is that there are many unknown factors involving EtG and elimination of same.
Since EtG synthesis stops at BAC=0 and it is eliminated exclusively via urine it follows that 1) it dissipates in urine with dilution and 2) each urination disposes of any remaining urinary EtG
present at the time.
Why EtG can be detected in urine many many hours after it is no longer detectable is blood (controlling even for urination) is left unexplained. Nonetheless, liquid consumption creates the need to void which in turn disposes of residual EtG.
I'm afraid that is all that is known of EtG elimination. The below link leads to one of the better and more realistic studies that may clarify further.
1)
Rosano & Lin (2008)
2)
Hoiseth, 2009