Looking on the internet deeply has found these results:

let the rainwater is the most popular phrase on the web.

let rainwater 18,520 results on the web	let the rainwater 189,800 results on the web More popular!
Some examples and use cases from the internet:	Some examples and use cases from the internet:
I begged my mother to let Rainwater keep his house.	All right, that's the rainwater barrels. I begged my mother to let Rainwater keep his house. The rainwater washes them down the hillsides as far as the sea. We should dig a big reservoir... that would collect all the rainwater. And all the rainwater that drops on the Mountain is actually accumulated. Well, maybe I'm angry because somebody stole all the rainwater that I collected. I saw you bathing in the rainwater. The city of Crestview has been declared executor for the Rainwater estate.

let rainwater

18,520 results on the web

let the rainwater

189,800 results on the web

More popular!

All right, that's the rainwater barrels.
I begged my mother to let Rainwater keep his house.
The rainwater washes them down the hillsides as far as the sea.
We should dig a big reservoir... that would collect all the rainwater.
And all the rainwater that drops on the Mountain is actually accumulated.
Well, maybe I'm angry because somebody stole all the rainwater that I collected.
I saw you bathing in the rainwater.
The city of Crestview has been declared executor for the Rainwater estate.