Pushing the 1/8″ polyurethane tube over the small barbed fittings correctly so that the joint is reliable without breaking them is not easy. It takes some practice, and as recommended in the installation instructions some heat, but not too much, is helpful to soften the tube end enough to do it. The tube must be pushed all the way as far as it can go up against the end.
If you bend the barbed pip, the fitting should be cut off and a new fitting used. Leaving enough slack in the tubing to make sure trimming a little back is not a problem is VERY important therefor.
Too much heat will cause the tube end to soften permanently, and the joint could then pop off under pressure. If a tube pops off under pressure, it is likely that the tube end was overheated.
To avoid an unreliable joint, use as little heat as possible, but there is a helpful tool – The Pincher Tool – you can make for yourself to help you grip the tube firmly and keep it straight, and therefor have less risk that you might bend the barbed pip. It is also possible to push the rube over the barb using this tool without first heating the end.
I was reminded of this tool by a family member of the original inventor of the Plant Booster, Al Muxlow. Al used to make these and give them to his friends. It really works like a treat.
The Pincher tool pictured below was made from a block of oak 1/2″ x 3/4″ x 1.5″. It was an off-cut of the same wood used to make fulcrum blocks.
A 1/8″ hole (same as the tube OD) was drilled down the centre and on one end a slightly larger drill was used to drill a little more than the length of a barb of a fitting to create a sort of flared effect.
The block was then cut in half using a hacksaw right down the centre of the hole. You will notice from the pictures that the finish of the wood is quite rough. That is OK, it all adds to the grip.
Using a staple gun two staples were shot into the block to hold the two halves together, but also to act as a sort of sprung hinge. The idea is that the two halves can be flexed apart to go over the tube (which rests in the groove of the drilled hole), and by pinching the two halves together the tube can be firmly gripped. The size of the block allows you to hold the tube straight, and thus allowing you to firmly push the tube over the barb with much less risk of breaking the small barbed fitting.
It is simple, but effective.