'there is no rush' is correct and usable in written English. You can use it when you want to let someone know that there is no need to do something quickly. For example: "Please take your time to think it over. There is no rush.".
There is no rush".
But there is no rush.
There is no rush, she added.
"There is no rush," the Knicks official said.
The Gore campaign, not surprisingly, says there is no rush.
With all that, there is no rush to make a move, or even arrive here.
With a lockout expected, there is no rush to name Walsh's replacement.
Being a terminologist, I care about word choice. Ludwig simply helps me pick the best words for any translation. Five stars!
Maria Pia Montoro
Terminologist and Q/A Analyst @ Translation Centre for the Bodies of the European Union