I was a trifle hasty when I said that I'd assembled the pump handle of the sprayer, apart from inserting the split pins, since that implied that the split pins were a trifling detail. In fact I managed to put them in the wrong places, and left out the metal washer, and it is a tribute to the quality of pin provided that I was able to straighten one of them out to extract it and then bend it again, twice, without the arms breaking. It was only when I got on to the hose and lance assembly, and looked at the baffling collection of assorted neoprene washers, that I found the attachment clip I'd been unable to locate to complete one of the previous steps:
7 Fit the attachment clip over the end of the handle and between the flanges of the green tank base.
Maybe you would instantly recognise an attachment clip when you saw one, but I didn't. It turns out to be a circular loop of plastic with a section cut out,that fits round the very end of the pump handle, and a bulge on the inner face that slots into the hole in the handle I thought I had to put a split pin through.
The instructions did not explicitly mention the neoprene washers, but I could see them in the parts diagram as tiny smudges approximately the size of a full stop. I asked the Systems Administrator, who said that every joint in the pipework of the spray hose and lance must have a washer, or it would leak. The washers all seemed to be of different sizes, and there were slightly more washers than joints, so it was not immediately obvious what went where. Or, indeed, how to get the washers on or in when doing up the joints. Eventually the penny dropped that, far from persuading the washers to sit snug up against the ends of the hose, I needed to ease them over the slight bulge at each end so that they would fit in the very bottom of the locking sleeves I was trying to do up.
Then I fitted the trigger back to front, before checking again with the diagram and turning it round, and the knapsack sprayer was assembled (apart from the metal washer, which I decided was not critical enough to be worth undoing the split pin for again at that moment. I know we do not have any spare split pins, because I asked the SA, who promised to get some). The SA suggested testing the sprayer with plain water, so that I could see where it leaked.
Reader, it did not leak. At all. Not from the hose, or the trigger, and no liquid bubbled out of the filling cap. And as soon as I released the trigger it stopped spraying, with no drips. It does not cover a very wide area even with the spray head set to maximum spread, but is so precise I could hit one emerging creeping thistle stalk in a border. Which is handy, because I have quite a few creeping thistles coming up. I was thrilled, and amazed, that I had managed to choose and assemble a piece of machinery that actually seemed to work.
It is designed to be worn on your back, and I probably will, although it does have a carrying handle, since that leaves one hand to wield the lance and the other to pump, and avoids the issue of putting the sprayer down on an area you have already sprayed, and then being unable to put it down anywhere else because it has weed killer on the underneath. The shape feels quite comfortable against the spine, although I will not fill it right up, because it has a capacity of 16 litres, and apart from the fact that I'm unlikely to need that much spray at once, it would weigh 16 kilos, which is ridiculous.
The SA was impressed that the intake to the pump was right at the bottom of the tank, but so it should be, otherwise you would not merely waste the last bit of each batch of spray, but be left with the problem of how to dispose of it, given that the correct way to dispose of excess herbicide is to apply it in the normal way, which is tricky if your sprayer won't spray. I am still not entirely clear about what is going on inside the tank, but I think the key difference between this sprayer and my previous one is that the domestic one worked by pressurising the entire tank, hence the infuriating herbicide bubbles that emerged around the tank lid, while this one contains the pressurised part of the system within the main body of the tank, so if there are any bubbles they are contained. I am worried about Maintenance and Safety instruction 3, To replace the cup washer on the piston of the air pump, but I'll cross that hurdle when I come to it.
Addendum The new kettle is very nice as well, fast and extremely quiet. It even has a padded handle, for goodness sake. Modern civilisation is wonderful sometimes.
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