On Sat, 07 May 2016 16:44:11 +0100, Chris Hogg wrote:

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.

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.

MM

The pipe from the timer should be acting as a plenum chamber, and
water should reach all six drippers at the same pressure, and they
should all drip at the same rate. If the water won't flow to all six
drippers, there has to be a restriction or blockage somewhere,

No, I checked every piece of pipe, every connector, every dripper.
There is no restriction anywhere.

either
at the input end, for example the outlet from the butt or the AC1
timer, or a blockage in the pipe before the last three drippers or in
the nozzles of those drippers themselves. AIUI the holes in the
drippers are small and easily blocked by debris. Check that they're
clear. There could also be a bit of crud stuck in one of the
connectors, possibly between drippers two and three. Is there a filter
in the system somewhere that might be doing its job so well that it's
become blocked?

No, I've blown through all the pipes and eyeballed the connectors or
blew through them into a glass of water to check for bubbles.

Do you get a good flow from the brass tap on the butt when you open
it, with nothing connected? Water should pour out. If it does, then
the tap isn't restricted or blocked.

Checked. It does pour out. It also pours out on the outlet side of the
timer when switched on. The flow from the first piece of tubing is
good, but not forceful as it's only 4mm approx diameter.

Attach the tubing running to the
water timer and set the timer to 'always on', but don't have any
tubing connected to the down-side. Water should pour out of the outlet
from the timer. If it does, the timer itself isn't causing the
restriction. Then connect the first dripper. Does water reach it so
that it drips OK. If yes, connect the second dripper, and so on until
you reach the point when an additional dripper doesn't drip. The
blockage will be in that section of pipe.

It reaches three drippers, but not the fourth. The first two flow
strongly, the third not so much. The fourth barely even drips. I've
tried a ring formation and an inline formation. No difference.

If there really isn't a blockage anywhere in the pipework or drippers,
another suggestion would be to make the feed pipe into a ring system.
Put a T-piece into the pipe just downstream of the timer, and connect
the blind end of the existing chain of drippers back into that T so
that you have something like a domestic electricity ring main. That
will allow the drippers to be fed from two directions, so if one leg
becomes restricted, the other leg will continue to supply the drippers
on the other side of the restriction.

I think the basic problem is not enough pressure. This PDF file from
Irrigation Direct has a lot of information about gravity feed watering
systems. It points out that to obtain a reasonable head of water (15
psi), the water butt would need to be 34.6 feet off the ground.
http://www.irrigationdirect.com/medi...arden-GFVG.pdf

or http://preview.tinyurl.com/z6lxpsr

MM