I'd seriously consider investing in a carpet washer. I use RESOLVE petsteam cleaner... spray the spots and put some into the water vent... wash the carpets twice. From then on, wash every accident... wash the tile/hardwood...
And do this at least weekly.
Keep a close eye on him... if you can't watch him---but him in the crate.
Some dogs don't like going on the pads? Some of them prefer going outside---outside works better with me... as I had more accidents when they were going on their pads.
If you take them out, when you are home take them out hourly---then slowly increase the time spand.
Also, crate when you leave him home.
hope that helped and sorry.
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Chrissy, Izze (Yorkshire Terrier),Molly & Suzie (Toy Poodles), Chachi (Chihuahua)