Construction workers laying a gravel parking area at the front of the house accidentally unearthed a Victorian dry-stone culvert, the original land drainage system long since overwhelmed by silt slipping down the hillside outside, but in pristine condition inside. Excavating the exterior of this provided the needed drain.
Now I had all the spring water from 30m of hillside collecting into a single flow, and somewhere for it to go, I could try again.
The fountain itself consists of three jets 1m apart, a first guess at 3mm nozzle bore took all the available water flow and sucked air, which eventually led to airlocking and shut-down, 2.5mm seems reliable enough. The initial plumbing was in place throughout the first winter. The pipes only froze once when intruders disconnected the water supply and I had to blowlamp the spray bar to get it started again. In the coldest part of winter we normally get a week or so when the average daily temperature dips below zero. During this time ice accumulates around the fountains, built up by the spray it develops into weird and fantastic structures (see photo).
The original design suffered from silting up: even after filtering the water the farthest nozzle from the supply would weaken and eventually stop, and could only be cleared by dismantling the whole system. So the second incarnation had a maintenance drain valve at the end of the spraybar so that water could be run right through to flush out the silt.
The solution came from an unexpected source. My mother is an amateur potter and offered to try her hand at firing a dolphin in her home kiln. I gave her some dolphin pictures from the Internet and she set about it. At first we had discussions about the technicalities of producing such a thing, which would be limited in size by her 30cm kiln, and would need a through hole for the nozzle. I did get a brief glimpse of half an unfired dolphin lying around her house, but then things went quiet.
The silence finally broke on my birthday when I received a set of three lovely glazed pottery dolphins as a present. At first I was terrified to leave them outdoors for fear of vandals either ripping them off or using them as a coconut shy. My original design had the nozzles well above ground spraying mostly downwards, but I redesigned the plumbing when I realised that setting them at ground level firing up the bank would make a much less tempting target, and would also reduce the amount of overspray on the garden. The new system has its pipes completely buried, and it loops around 180° so that the drain valve also runs into the culvert. I glued the dolphins to 8mm flexible copper nozzle pipes and settled down to watch the reaction of the local Neanderthals.
Nobody made any serious attempt to remove them or to damage them (and I did get several compliments from passers-by), but they soon learnt the flexible nature of the pipes and several times I came home to find the jets redirected onto the gravelled parking area, making a nice puddle. After a few such incidents the pipes began to kink and crack, so I replaced them with regular 15mm rigid copper pipe. This meant digging pits in the earth to resolder the pipe joints and aligning them accurately, as I could no longer redirect the nozzles by bending, but with the old flexibles as a guide that wasn't as difficult as it sounds. The dolphins were secured with expanding foam sealant. The next attack cracked some bits off one of the dolphins but didn't shift anything.
This held the vandals for nearly six months. Then one day the dolphins had gone. So now we are just back to pipes, but the fountain still runs reliably, the filter needs cleaning every few weeks, the interceptor needs emptying every month or two, and after storms. Occasional leaf fragments manage to get into the line (while cleaning filter?) and block the jets and sometimes worms crawl though the filter and get extruded (Yuk!), but a combination of poking and flushing always clears them.