What to do if plumber finds surprise and cannot finish the job?

[Alex K.]

So I had a leak under the slab foundation of my 4-plex in the hot water line. I paid a plumbing company to find the location of the leak with a listening device. The guy gave me a bid of $1525 to fix the problem the same day. It included concreting over the hole after the repair was made. Keep in mind I have 4 units without hot water and he was the only plumber that would do it before the weekend (It's Friday morning). So I agreed.

4 hours later his guys show up and they jackhammer the foundation to find a 18 ft long tunnel big enough to crawl in, and a leaking PEX pipe in there, obviously done after it was built. Someone had tunneled in from the edge of the foundation to fix a prior leak and had only bothered the fill in the opening. I went to Lowes and bought the PEX parts and the plumbers fixed the leak, restoring the hot water. They left without filling the hole. It was 2 guys there for 3.5 hours.

So the job of filling in the hole was much more than the estimator had expected. I did it today with a friend and it took 3 yards of DG and a lot of dirty work.

The question is, how much should I pay the plumber? They didn't charge me that night, saying I could talk it over with the boss on Monday. They did come out the same day with the jackhammer and restore the hot water. But I had to do the rest myself and it was a big job. I'm thinking no more than $1000. Opinions?