Same advice I gave in the cat pee thread:
If the carpet is synthetic, not wool or natural fiber, you could try hydrogen peroxide. Peroxide will bleach natural fibers and may bleach some synthetics. You can inject it with a syringe or a marinade injector and that will help get it into jute backing and carpet pad.
If this has been a long term problem, the urine is in the carpet pad and perhaps subfloor by now. Commercial carpet cleaners will pull up the carpet, spray the jute backing heavily. They will cut out the section of urine soaked rug pad. They then spray or possibly replace the subfloor and paint it with a sealer like one of the Bullseye shellac products. If extensive sections of pad or subfloor are soaked, then replace an entire room is what you are looking at. Replace pad, put carpet back down, then clean carpet.
In many cases, the carpet can be salvaged, but if you’ve got an entire room that’s used as a toilet, and you are replacing all of the pad and subfloor, get new carpet.
I have a Bissell ProHeat 2x, older style, model 9400 or 9200. And cats. First, I treat rug with peroxide, try to get it immediately before urine starts to stink. Blot, peroxide. I may then use enzyme, depending on whether the peroxide seemed sufficient. Either way, I use generous amount because volume needed = volume of urine. This I can see being a huge issue with dog urine. I would use my nose, find all pee spots, and inject the hell out of them with peroxide as a stopgap or first pass. The Stinkfinder is a weak blacklight that is of some value. But commercial guys have higher power Blacklight’s that do a much better job. The enzyme stinks, so I always have to clean a carpet or spot-clean after. I have pale beige carpets, so I can get away with brooming carpet deodorizer, Arm & Hammer, into carpet after and just leaving it until I vacuum.
Regardless of carpet cleaner brand, you need to first kill the urine and then clean the carpet. Otherwise, you just flood the pee everyplace over a wider area. And you need to EXTRACT virtually all of the liquid out of carpet when you clean, and RINSE with clean water and extract again. Don’t leave dirty water or soap or diluted pee in there. Not all commercial carpet cleaners are fastidious. You need to make sure that the one ya use doesn’t leave dirty or sour or contaminated water in your carpets. In my experience as a DIY-er, the commercial guys used a whale of a lotta enzyme and left boatloads of dirty water in the carpets, and the carpets stank with a different odor and weren’t really clean. And the enzyme makes its own stink later, and you can expect to have to do a standard soap 'n water 2nd cleaning. My Bissell pulled black water out of my carpets after the pros were there. Maybe the pros used recycled dirty water? If I use pros here agin, I will watch them closely.
Extracting takes a long time with the Bissells and Hoovers. You may want to rent a carpet cleaner to get the job done faster. But usually, you have to clean those machines before you can clean your carpets, lol.
