adult dogs urniating in house

Question
I currently have a 4 year old Shih Tzu, a 4 year old Shih Tzu mix raised together from puppies, and and adopted 8 year old pomeranian.  One or all 3 are urniating on the side of my couch and chairs, on any bag in the room, the side of my bed, and probably more places that I'm unaware of.  They have access to go outside via a doggy door at any time, plus I let them out frequently when I am home and they express the need to go out.  I now have them penned up in the kitchen while I am at work for 6 - 8 hours a day, with absolutely no accidents, yet when I'm home and they have access to the rest of the  house I find unrination on items.  I have yet to catch them.  They all get a lot of attention equally, I try not to show overexcitement when coming or going and knowing that it is a behavior, I'm not sure how to deal with it.  My parents of the same issue with their 5 dogs and then when mine join them they get even worse.  I hoenelsty cannot remember how long they have been doing this, it seems like forever, but I don't think it was prior to adopting the pom last November.  Any help/information would be wonderful.  I do want to mention that they all just had a clean bill of health at the vet today, so it is also not a medical issue.  Thanks in advance for your advice.

Answer
If any of them aren't spay/neutered, that may help.  You can't add a third dog without having at least 2 of the same sex.  Even if fixed, they may still be competing for dominance and marking in the house.  Providing good leadership yourself may help.  The key to most behavior problems is approaching things using the dog's natural instincts. Dogs see all the people and dogs in the household as a pack with each having their own rank in the pack and a top dog. Life is much easier if the 2 legged pack members outrank the 4 legged ones. You can learn to play the role of top dog by reading some books or going to a good obedience class. A good obedience class or book is about you being top dog, not about rewarding standard commands with a treat. Start at http://www.dogsbestfriend.com/ For more on being top dog, see http://www.dogbreedinfo.com./topdogrules.htm

The only other thing you can do is keep them shut up in the kitchen as you are when away, and keeping them in the same room as you and keeping an eye on them all the time.