[Auntie Rain]

Am looking to build raised beds and was thinking it might be a good idea to lay a network of pipes then fill over to create raised bed. Then I can irrigate my new bed using the buried pipes. I am expecting to use less water as there will be almost nil evaporation and it would encourage deeper root systems than surface watering....

Does anyone have any experience of this? What do I need to think about?

TIA

AR

[Trillium]

I've not tried this idea myself, but first of all I'd worry about seedlings - their roots would take a while to reach any damp areas, particularly as all moisture would mostly head downward rather than up. You'd be dependent on rainfall, which could defeat you some years.
Any buried piping would need first to be covered in long term mesh fabric that wouldn't allow mud to plug up openings. And it would be difficult to determine just how moist your deeper soil would be short of digging up patches to check.

Personally, I'd lean towards surface emitters or soaker hoses covered with mulch like straw to hide them and prolong their life. They're easily moved for prepping soil and checked for functioning.  Mulch would also reduce your weed problems. A few hours (on a line timer) once a week would deeply soak your soil so that all ages of plants could benefit. You can even hook these up to water butts on a line timer. And any malfunctions are easily dealt with.

[waddecar]

One of my raised beds has a piece of gutter system down spout with an elbow at each end to provide access for a hose - hardly a network! I drilled many holes in the pipe for water to soak away. I probably drilled too many (or too large) holes because the pipe is impossible to fill (its only 4m long).

I garden on a slope so my raised beds are a bit like terraces and (I find that the water drains out of the bed as fast as I put it in. Pipes still there but not used it for a year or too.

It is probably my execution that is flawed but it may be the theory

good luck