Sonorous drainpipe with snow melting in it

This sound is produced by a large fixture halfway down a thick and leaky drainpipe on an old building. It snowed the day before this sound was heard, so perhaps it is produced by something melting slowly further up the pipe? The recording was made by placing the EDIROL R09 on a ledge part-way up the pipe. A very slight high-pitched/treble-heavy trasmitted static sound is coming from further up the street, where there was a broken intercom.