While I like SQLAlchemy a lot, it has to be said that it leaks like a sieve.
Personally I think the problem is not that ORMs are leaky abstractions, it's that they often pretend not to be. SQLAlchemy just leaks unapologetically, if you struggle with ORM you can drop right down to using an DSL to construct SQL or just write SQL directly without feeling like you have to fight the ORM and mess with undocumented internals you shouldn't be touching.
