It is forbidden min haTorah to read Krias Shema opposite a stream of urine or next to urine that smells. But if it is collected in a puddle or in a vessel and does not smell, it is forbidden mid’rabbonan. The rabbonon said that a revi’is of water can nullify the urine whether placed before or after the collection of urine. (ShA 1 – MB 2)
If the urine is putrid, then only enough water to remove the smell will work to nullify it. (MB 2)
If the vessel is designated for urine, even if there is no urine in it you may not read Krias Shema next to it – water will not help. (ShA 1 – MB 5)