To the OP and everyone else the waterpump is the same for all the JTD multijet engines, 1.9 JTD 16 and 2.4 JTD 16v, as found in the 147/156/GT/159/Brera/946 Spider. Current mean average failure rate in the waterpump thread in the 147/156/GT lounge is around 56,000 miles and just over 4 years.
It is strongly recommended that you get all the timing gear plus waterpump changed on these engines either by 4 years or 48,000 miles, whichever occurs first. My local dealer has had lots of failures with this pump, especially on the 159 1.9 JTD 16v, and recommend that the pump is always changed with every belt change.
Alfa_Forza, I'll add you to the 'near misses' table in the sticky thread. You're now the second 159 to join that thread, if more are noted I'll ask the mods to transfer the sticky from that lounge to the engines lounge, where I suspect it should belong anyway.