On Sat, 07 May 2016 15:32:55 +0100, MM wrote:

I'm trying to set up a home-brew drip feed irrigation kit for 6 tomato
plants. I've already got a lot of suitable tubing, the T-pieces,
connectors, drippers etc. The water feed is off a new 230 litre water
butt to which I have attached a brass tap instead of the black plastic
one. To the tap I've connected a Hozelock electronic water timer
(AC1), which Hozelock customer services confirmed will work with a
water butt, and it does.

So I placed the tomato plant pots close to each other and close also
to the water butt, then ran the tubing from one to the next. I then
switched the AC1 to "always on" for testing.

The problem is that even when the butt is brimful it seems to have
only enough head of water to feed three of the drippers. And even then
the third dripper furthest away from the butt dribbles rather than
drips. The water will just not flow around the circuit to all 6
drippers, and I can't understand why not! I even tried sucking on the
little pieces of tube as if to "bleed" them of air. No improvement.

Are these drippers 'designed' to be run at mains pressure? If so it
may simply be that the ones nearest the butt are working at all? Are
they adjustable?

The feed to the first 2 pots is excellent and the water drips really
nicely. So it would work for 2 plants, possibly 3. But where am I
going wrong? The water butt is mounted on the typical black plastic
stand, which is about a foot off the ground.

And presumably the drippers are in the tops of the pots and so also
off the ground by some amount, so you are (just) relying on the head
of water in the butt to provide the 'pressure', rather than the height
of the butt above the ground?

How about taking the drippers off and setting the timer to run for a
shorter period? I see no reason with that setup why the water
shouldn't make it to the last port, but only if there isn't a large
amount of back pressure required to overcome some of the drippers?

I know when I kept tropical fish is was difficult to balance any
air-bricks or air powered filters if the air hose was in a single line
(Tee'd from the same bore hose). So I made up a plenum chamber from a
tin can with some brass tubes soldered in and that made things much
easier. It was interesting to see this can 'inflate' slightly as the
pump brought the system up to pressure (I had one of those induction
motor piston pumps and the plenum also ironed out the pump 'strokes').

Assuming all your drippers are supposed to be the same, it would be
interesting to see how they compared when they were all fed in
parallel, rather than series?

Even when running mains pressure feeds to my runner bean plants (also
via a Hoselock timer) it was interesting to see the wide range of
'jets' you saw across all the outlets, even when being fed from a
common larger bore hose.

Cheers, T i m