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I am in the process of installing a sprinkler system using a commercial controller. There is quite an extensive area to be covered, and I am wondering whether, for the further-away sections, it would be preferable to have long pipe runs (with possible loss of water pressure) or long cable runs (with possible loss of voltage).

Plan A

Plan A

Blue lines are water, red and black lines are the wiring.

In this plan the solenoids to control the water flow are located near each other, with a 4-core wire controlling them (one per solenoid plus a common). Some sprinklers however would require a fairly lengthy pipe run. The plan isn't to scale, but I have indicated distances on it.


Plan B

Plan B

In this plan the solenoids are located remotely from each other (they would each need their own nearby water supply of course). I would now need to run a pair of wires to each one, with the common wire shared. My concern with this is that with this arrangement the common wire in particular might act as an aerial and possibly pick up static or pulses which could affect the controller's behaviour.

These are all outputs from the controller, but still.


From an electrical point of view, which is preferable? Plan A or Plan B? Or won't it make any real difference?

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    \$\begingroup\$ "installing a sprinkler system "....... lawn or fire? \$\endgroup\$ – DJohnM Dec 16 '17 at 0:24
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    \$\begingroup\$ Does the sprinkler come with an installation manual? Does it suggest a maximum run length for wire? My initial bias is to run long lengths of wire. Not sure I can justify why. That is just how it seems to me. \$\endgroup\$ – mkeith Dec 16 '17 at 0:42
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    \$\begingroup\$ It's for watering plants, so neither lawn nor fire. Basically the water pipes run to various sprinkler outlets around the garden. \$\endgroup\$ – Nick Gammon Dec 16 '17 at 1:00
  • \$\begingroup\$ There is an installation manual which is surprisingly light on technical detail. There is no mention of suggested wire gauges, voltages (although I assume that it is a standard 24VAC) nor maximum wire lengths. \$\endgroup\$ – Nick Gammon Dec 16 '17 at 1:00
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    \$\begingroup\$ Having built a number of these I'd suggest that you put all you valves in one central box. One place to turn the water supply off and one place to run your valve power (probably a 24 or 32 volt safety transformer with wire to the box). If the controller is in the box then you only have a signal cable to run. Don't forget to slope the delivery pipes so you can empty them in case of freezing (you live in Melbourne, right?) in the winter. \$\endgroup\$ – Jack Creasey Dec 16 '17 at 1:02
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I think I would prefer to have the solenoid valves in one location, preferably an indoor or weatherproof location.

You will have the same pipe lengths wherever you put the solenoids, so you will have to allow for (or compensate for) pressure loss regardless of where you put the solenoids.

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  • \$\begingroup\$ The OP implied that he had separate sources of water for plan B so the pipe lengths would not be the same, the only apparent advantage of plan B over plan A. How he does this we don't know; we don't even know if this is a lawn sprinkler (for which separate water sources seem unlikely) or a fire sprinkler (where separate water sources might be possible). \$\endgroup\$ – Barry Dec 16 '17 at 0:44
  • \$\begingroup\$ Yes, the places in question might be regarded as "front yard", "back yard" and "side yard" each of which has a water source. I suppose in a sense the water still has to get to each place so perhaps whether it is before or after the solenoid is not a big issue. \$\endgroup\$ – Nick Gammon Dec 16 '17 at 0:50

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