I noticed yesterday there was a little pool of water in my crawl space. Today with the kitchen faucet running, I discovered why. This plastic pipe is about 3 inches diameter and is cracked pretty much along half the circumference of the pipe. What will it take to fix this? Can it be sealed? Or how much of the pipe would have to be replaced?

Please dumb down answers as much as possible. My husband and I know nearly nothing about plumbing. I just hate broken pipes!

Back up and take a picture from a bit further out. Can't see this too clearly but it looks more like a chromed brass 1 1/2 drain pipe. Does it go straight into the wall after the trap or does it come straight down from the sink to the trap? The trap is the S or J shapes thing under the sink.

My answer assumes that the pipe is in the crawl space, not under the sink.

This pipe is known as ABS pipe. Here's what you do...

Buy as short a piece of the same size pipe as you can. You'll probably need about a 4" long piece.
Next, buy 2 "no-hub couplibgs" that are made to fit ABS pipe.
Use a hack saw to cut out a piece of the broken pipe. It needs to be long enough to fit the NH couplings and a new piece of pipe.
Cut your new piece of pipe about 1/4" shorter than the section you removed.
Slide one of the NH couplings onto each end of the remaining pipe. You might have to work them around, fold them back, etc. to fit the new piece of pipe in.
Install the new piece of pipe.
Use a nut driver to tighten the hose clamps on the NH couplings. Make them pretty tight (or buy the special ratching torque wrench that automatically ratchets when you reach the correct torque, not really necessary here).

That should do it!

I like Hortons answer. If the rest of the pipe isn't faulty that's exactly what I would have advised.
I'm curious though. Any idea why the ABS plastic cracked in two? Damm! But those breaks look like cuts.(see image) Back to you, Tom

Moragill,
Please post a new picture as Ballengerb1 suggested, we will know where the pipe is located, is the pipe coming down from the sink or it goes to the wall, if it is coming down straight from the sink you can remove and replaced it with a new one, if it goes to the wall you can repair it as Hontni suggested, or you can buy a repair kit see the link below, good luck.
John

PlumbingStore.com - Pipe and Hose Leak Repair Tape

I see what you mean about needing to clarify. It's difficult to get an accurate picture. This pipe originates 5-6 feet to the right of this crack. At that point, there's an elbow joint connected at the ceiling (next to the wall).

Hontoni told you what to do...

Now, I am just curious why that pipe snapped. Is it connected to Cast Iron pipe ? It appears that something heavy is pushing on that pipe on the left. Find out what it is and fix it. Once you repair the break, support the pipe on both ends so it doesn't happen again.