You kinda have to understand the marking impulse to solve this problem. There are several reasons a dog marks. I have a 5-year-old un-altered bichon frise who marks specifc spots in my house.
Reasons for the marking impulse:
1.) Establish a territory - a dog's primary sense is his sense of smell. They can communicate between packs through the unique pheromone present in their urine. Instead of having to do perimeter rounds to protect their territory, an assertive dog will leave their pheromones announcing their claim to a territory. Note that they will only protect the areas that are important to them that has a consistent source of food and water and small enough that they can adequately defend it. So more than likely, if they feel inclined to claim a territory, it will be inside your house, within "defending distance" to the food bowl and their sleeping area. A dog who feels he has to mark his territory is a dog that does not have enough confidence in his pack leader (you) to defend it. This is the reason my dog marks. My dog is a very insecure dog with an acute case of separation anxiety. Marking territory makes him feel better. I tried to correct the behavior by providing positive reinforcement, confidence builders, clear structural hierarchy, etc. It's not working for him. So he wears a belly band when his anxiety level is high and he stays in the crate when we're not home.
2.) Establish pack leadership - a dog also communicates his age, gender, and pack status through the pheromones in his urine. The marking impulse also gets triggered when the dog wants you to know that information, usually as a sign that he is getting ready to challenge the hierarchy. A clear structural hierarchy - making the dog understand without question that he is never going to be pack leader - can correct this behavior.
3.) Announce his breeding availability
This usually happens around the time the dog hits puberty. Once this marking behavior is established, neutering the dog has a lesser chance of correcting the behavior without additional behavioral correction.
4.) Medical issues such as urinary tract infection, hormonal imbalance, etc.
An English Bulldog matures slower than most dogs, so 15 months of age is about that time. Tank could be expressing territorial claim, pack leadership challenge, and a mating call all together at the onset of his maturity. Neutering him may correct the marking impulse or it may not. You may still have to do some behavioral correction according to the reasons presented above after he is neutered. It's not too difficult to do unless you have a dog like my bichon who has psychological issues. Usually, a strong pack leadership is all that's required to curb this behavior. Things like making the dog sleep in his crate/bed instead of your bed reinforces your status on top of his, making him wait for his food and water, making him "work" for treats, making him wait for you to go through the door before he goes through it, not allowing him to walk infront of you during walks, etc., etc. And making sure that there's no trace of urine smell left in the house at all because smelling their urine would trigger the impulse to make the smell stronger. Very strict supervision during the correction stage (may last for more than a month) may be necessary because one marking incident could undo the entire training process.
But, if you have something like my dog, you may need physical aid in addition to behavioral correction. I take my dog out to pee for an extended time because he would hold his pee. I taught him to pee on command. So, I would give him the command to pee repeatedly until I see him lift his leg and nothing comes out before I let him back in. Then he gets his water on a schedule. And when his anxiety level is high, I put a belly band on him - it's this piece of cloth that you put a disposable padding on that would wrap around his belly covering his genital for extra protection.
And a few words on neutering: There is no scientific evidence that shows that neutering can stunt a dog's growth or change his personality. The only thing that has scientific backing is that it will reduce a dog's desire to find a mate.
Hope this helps!
That look is relief. ha ha ha ha 
