In uk.d-i-y, wrote:
Despite the title this is mainly a 'plumbing' question...

I'm trying to put together a low-cost simple garden watering system
that I can bury a couple of inches under the soil. Gardena and
Hozelock both do watering systems, but the delicate drippers and
sprayers are prone to blocking, are fiddly to set-up and have to be
above ground where they would be vulnerable to attack by my rotary
mower. They're also fairly expensive. I'd prefer to lash-up a home
built system using 15mm and 22mm plastic pipe to feed lengths of
'soaker' hose, all of which could be safely buried out of harms way.

Has anyone already done this?

Yes, but only as a temporary (three years) measure while plants were
getting established in a new bed.

Would you recommend Hep2O for shallow
burial, or would I need to use the blue (MDPE?) pipe instead.

I used ordinary green hose pipe, and as I wasn't overly bothered about
appearance a lot of it ended up on the surface.

Has
anyone found a plumbing connector that would be suitable for joining 15
or 22mm plastic pipe to short lengths of 'soaker' hose?

With ordinary hose I used plastic push-fit connectors of the sort used
in those expensive Hoselock/Gardena systems you mentioned earlier.

I haven't
bought any samples for testing yet, but soaker hose *might* be the
right sort of size to jam over 15mm pipe. Alternatively, maybe it will
accept one of those reinforcing inserts and fit a Speefit or Hep2O
connector :-) Either way, I'm reluctant to use something like
jubilee clips because they'll rust away very quickly.

I used stainless jubilee clips, which survived just fine.

To get round the
problems of freezing in winter, I'd probably blow air through the
system at the end of the season to push most of the water out.

I didn't bother flushing for winter and the system came to no harm. It
was all flexible enough to cope.

Soaker hoses need good pressure, and with a large area to cover, I found
it necessary to run several systems each with their own timer,
programmed to come on at different times of day.

--
Mike Barnes