Foundation butt joint?

[Jared Guess]

When a new foundation wall is butted next to an old one how is it tied in to the old wall?
I am guessing that they should connect the two with some type of anchors but what are they suppose to do to keep it from leaking when the new concrete sets up and draws away from the old? Fill it like a settlement crack??
I would give you a picture but it is late and it takes more than six hand movements to figure out how to insert the darn thing.

[Matt Fellman]

I don't think anything is typically done... it's just an opening. If there's a lake on one side and that crack is the only thing to stop the water you have bigger problems.

I had an addition put on my house last year and there was no tying of anything. Structurally, there's no need... each section must stand by itself.

[Markus Keller]

It would depend it bit on why the adjoining new wall is being built. If it is being built for structural support along side an old stone or brick foundation wall, I've seen guys tie the two together with rebar. Seems dumb to me for various reasons but that's another story. If it is a concrete foundation that has failed, drilling and inserting rebar to the the old and new together is common around here.
In your case though, it sound like the wall is being poured to stop water leaks? 'Water leaks into our basement, what should we do?' Well Sir, your foundation wall is old, we can pour a new one and that will help. That will be $10K, check please. If that is the rough scenario, pouring a new wall may not have been the best course of action. Tying the old and new together really is irrelevant.
More info please.

[Jared Guess]

Thank you for the replies,
The newer foundation wall is for an addition. No problems with the old foundation wall. But now there is water penetration in the addition crawl space from that joint.
So is it safe to say they need to fill it as if it were a settlement crack?

[Markus Keller]

That changes things a bit. Typically around here one drills short rebars into the old wall that protrude out and into the new wall pour to tie things together. The joint between the old and new isn't necessarily water proof or a major source of leakage either, depends on various construction factors. It isn't uncommon to caulk or otherwise seal that joint either.
However, you keep mentioning settlement crack. That doesn't sound good. You may have quality control issues with the foundation pour. Talking about settlement cracks in this situation isn't really normal. How large of cracks are we talking about here. Anything more than 1/8" +/- due to shrinkage from the new pour may indicate other problems. Were proper footers poured, did they cure long enough, were footers placed on undisturbed soil, etc?
The other issue you seem to have is water management. Sealing this crack probably won't last long if you have water quantity, as it sounds, coming in.
What's up with the downspouts, how is the grading to the addition, was it properly backfilled or just whatever dumped back in the excavation, what is the source of water - rain, ground, pond, what; can it be managed? These are all questions to ask in order to provide a 'proper' long term solution.
If you want the DIY fix, gob some caulk on it and high five yourself.
You aren't really providing sufficient info to provide answers instead of more questions.

[James Duffin]

I would not recommend a repair method. If you recommend that they need to fill it as if it were a settlement crack and it still leaks then you are on the hook since you recommended a repair that did not work.

I would report what is saw....that there is a crack that is allowing water to enter the crawl space. Then I would say it needs to be repaired by a waterproofing contractor.