* our fault, not theirs!!
click to enlarge
Rainwater then flows down a sloping (red painted) stone and onto a less steep ledge which provided a walkway round the tank for the bold / brave or barmy:
at the edge of that ledge most, but by no means all of the water drips off and falls to the ground, well clear of the tower walls below. Remaining water has further opportunities to drip away as more overhangs are encountered:
These pictures were taken during heavy rain this afternoon and it can be see that the combined system is very effective indeed in shedding the water - to the extent that the tower walls are perfectly dry:
The problems only arise in driving rain when some of the rain makes it to the lowest of the ledges, immediately above the square support or dentition stones. Any water that does not fall off then gets blown against the top of the wall itself. The increased wind pressure outside finds any crack in the mortar and water gets sucked towards the reduced air pressure within.
Nowadays a drip groove cut into any or all of the overhangs would deal with the problem most effectively. There appear to have been attempts to deal with the situation by applying tar or bitumen to the stonework between the dentition stones but this, besides being unsightly, has failed:
In short, what appears to be a decorative plinth of the tower is in fact a cleverly devised and most effective way of shedding the water away from its upper walls, most of the time.
The remedy seems to be to remove the old tar (much of it scabbing off anyway), to rake out the mortar between the dentition stones and to replace it with the sort of filler that was used with success between the iron tank and the tops of the plinth stones, in a matching colour.
Unless you have any other ideas????
Do please comment below.