Pet urine and rugs are a bad combination. The urine goes on warm and acidic, penetrates the wool fibers, and literally redyes the rug.
Old pet stains become alkaline ... and this leads to color fade and the release of dyes in these areas. A rugs with stable colorfast dyes will bleed on you if it has old pet urine stains - and there is no way to stop that. Even using a dye stabilizing solution on the rug - you will stabilize the dyes in all the areas outside of the urine-affected areas ... but those pet stained areas will likely bleed on you.
So ... always get a release on the rug bleeding during cleaning due to the pet urine.
That said - after you have the release - the stains are often permanent, depending on the rug, and it is our policy to always say they are permanent that we can only guarantee odor removal ... then if the stains work their way out, we have underpromised and overdelivered. The rug is damaged. It may be a $10,000 rug ... but it is NOT after pet urine is put all over it. It is a pet toilet that someone else is not going to pay $10,000 for. There needs to be a note that the rug was damaged before you began your work, and that you will do your best to clean the rug safely and remove the pet odor.
So let's talk about pet urine odor removal - and some tips for those of you who do NOT have a rug plant and cannot thoroughly flush out the rug with a bath.
This rug with the photo above is a Tabriz rug, with old pet urine stains - the reds have bled in this area AND the reds in the rest of the rug are also not colorfast - they are fugitive dyes.
In our rug plant on our cement floor (with a raised edge all around so we can close the drain and soak a rug) - we begin by flooding the rug with acetic acid 3-4% ... we do this to stabilize the dye (in the areas without the urine - because the dye has already bled in those stained areas - and we have the release acknowledging this), and also because soaking the rug in acetic acid will penetrate the middle of the rug and help to release the urine salts within the foundation fibers and help us flush the urine out of the middle of the rug.
Many wool rugs have wool fiber knots wrapped AROUND cotton warps and wefts, and cotton is absorbant - so if you are surface cleaning both sides of the rug, you are not reaching the innermost cotton strands which have soaked up the bulk of the urine. That's like cleaning a used diaper with your upholstery tool on both sides - the inner absorbant part is where the problem is.
Then we follow with our shampoo process, rinse, and put through the wringer to remove the water. We dry our rugs flat with air movers (I love my Airpaths), and then do any finishing touch-ups.
But ... let's say you don't have a big wash floor and no wringer or revolution to remove the bulk of the water QUICKLY (which is what you need to do when you have rugs that are BLEEDERS) - how can you surface clean the rug and do the best you can on removing the urine (and the odor)?
What I'd suggest is to set up a makeshift wash pit using some PVC pipe and plastic (not dark - go clear or light and thick like a tarp). Here's a photo of one example:
If you soak a "bleeder" this much, you will have problems - so what can you do? (This particular plant has a wringer, so after soaking the rug goes straight to water removal.)
What you need is white vinegar,some foam pad (for compression) and a Water Claw. Lay the rug out, identify the specific urine affected areas, and do the following:
1) Mix vinegar with water 50/50, and saturate the spot with the mixture.
2) Place the pad under the wet spot, and use the Water Claw to pull out the urine. If the water is coming out yellow - you are getting it out.
3) Repeat until the water is not yellow - move to next spot.
4) When all areas are handled - then move ahead to clean the rug with your usual cleaning steps ... though, I'd suggest adding Bridgepoint Hydrocide or another odor-removing solution to your shampoo to help.
Extract - dry - and make sure it is 100% dry by using a Moisture Sensor poked into the middle of the rug to verify this (do NOT use the touch test as the wool will often feel dry but the cotton inside can still be damp and you cannot "touch" that).
The Water Claw was made for restoration work - but in this scenario it is a great tool to work on specific problem areas. It also can remove water from a rug after cleaning - but that can take a long time. The medium size works best, and use CLEAN pad underneath for the compression. I've tested the Claw in workshops, and the Extreme Extractor - the Claw pulled out more than the EE - but I know that's because it's a rug ... the EE works best in flooring extraction.
I have not tried the DriEaz Rover yet, but am eager to test that. For those of you who cannot afford yet a wringer or the Revolution centrifuge (spinner) - and you do restoration - it is ice to be able to use the tools you already have for rugs.
Hope that gives you some ideas and strategies for urine removal when portable cleaning rugs at your shop (do not ever use a pit in a client's home ... just FYI ... that seems obvious, but I thought I better say that since McDonald's has to write "do not spill hot coffee on your lap" on their cups - well, I better be safe here too - LOL)