Cause
Miscommunication! Your dog is just trying to be ultra-polite. Unfortunately, it is all too often interpreted by us humans as "I know exactly what I'm doing and I'm doing it to tick you off." Consequently, the owner punishes the dog. Causing the dog to think the owner did not understand his very clear signal of submission. Next time he tries harder to communicate by urinating sooner and more profusely. The owner seeing defiance punishes the dog more intensely.... and on and on we go. Some breeds, American Cocker Spaniels and Golden Retrievers in particular, can be especially prone to this problem.
Corrections
NONE! Any correction will make this problem worse. Since she is only trying to say "I am a small dog, please don't hurt me" if you correct her, she will only try to say that LOUDER by peeing more. Oh no!
Common Mistakes
People get annoyed and scold or spank the dog. Punishing or correcting a dog for submissively urinating is like throwing gas on a fire to put it out. The only way to solve this problem is to ignore it, train your dog using positive methods and wait. Over time, it will decrease. Slip once and show your displeasure and it will take you twice as long next time to get him dry.
If your dog has been intimidated in the past either by you or a previous owner, he is peeing in an effort to avoid punishment he thinks may be coming. This type of submissive urination is usually person-linked, many times to men in general or to a male in particular. All yelling at or physical corrections must stop - from this moment on.
Some dogs do this with one or two people who, while never harming the puppy, the puppy sees as leader types and then pees as a sign of respect. This generally passes.
Further Advice
If you know your dog's trigger situations then ignore your dog when you are in them. And we do mean ignore - no eye contact, speaking to, or touching. Just go about your day as if nothing is happening, and hopefully it won't be.
If your dog is a doorway puddler, instruct guests to ignore your dog for the first ten minutes or so they are at your house. Then allow the dog to approach you, while you are squatting and turned away from dog. Do not bend over or reach toward the dog as this will cause the floodgates will open.
It is hard to be fearful and anticipatory at the same moment so distracting the dog with a biscuit when you enter the house can avoid mishaps. Keep a stash by the door and when you enter toss one to your dog. Ignore the dog and continue. Over time, your dog will come to look forward to you coming home, instead of being anxious about it.
And, lastly, training which focuses on praise and enthusiasm, builds canine confidence. If your dog knows exactly what you want, exactly how to please you and exactly what wonderful things will happen when he does, he will have no doubts. A dog with no doubt is a dry dog.