Stop my 1 year old silk terrier from pooping in the house

Question
My husband and I adopted a 1 yr old male silk terrier from a shelter.  He is a very good dog he is mostly house trained but from time to time he will poop in the house.  We let him out as soon as we get up in the morning we come home at lunch and let him out. We take him for walks.  Alot of times when we take him out he will not go poop we just don't know what to do. We keep him in the sunroom when we are not home. We also have gates up to keep him in 3 rooms when we are home. We do not know when he goes poop since we have the gates up . The other thing is he will not bark when he needs to go out.

Answer
Hi,
I need to know when you feed him for one thing; that would help a lot.  For now, when you are home, he is only allowed to be in one room, the room you are mostly in.  Also, make sure in the morning he goes out twice.  He has been holding his bladder all night so when he empties it, the kidneys say,  "Oh I can now send more urine (that I have been holding all night) to the empty bladder."   This will cause him to have to go again.  
Barking to go out:  Lots of dogs won't do that.   Teach him to use a bell.  Hang a bell on the door, (at a height he can easily reach) arrange it so he hits the bell when you say to him "Do you want to go out?"  Give him a treat every time he hits the bell.  You will have to kind of arrange that he hits the bell in the beginning, until he gets it himself.
Get back to me on the time you feed and I will figure more out for you.
nancy