Whose responsibility to empty septic?

[Marci Stein]

I know I messed up by not addressing this issue in the lease.

For those of you who rent out homes with septics, 

do you have the tenant pay for emptying it or do you pay?

Will it be too late to add it to the lease upon renewal? 

they have been there 5 years without a septic cleaning. How often should it be done with 3 people living there?

Many thanks!