drip system advice - quantities/running times

REMF33

I should have asked this weeks ago but I know it's a bit of a 'how long is a piece of string' question, so I delayed.
I have set up drip systems from a water butt for my raised bed. The beds are about 1mx1.5m. My system is supposed to deliver just 180ml per hour. There are two systems, each running off their own 200l (ish) rain water water butt (hope they don't get clogged...). One bed is full of beans. The other less full.  I will be away for 10 days. 
The water timer can be set so that it runs from once an hour to once a day, plus once a week.
I am just looking for advice as to a very rough estimate for how long to water for i.e. how much water to deliver.
I know I should have done a trial run, but water is precious and I've been watering my beds using rain water collected in buckets during the deluge a week ago for the last week. (Water which is very mucky so didn't want to use it to top up the water butts... and potentially clog the systems.)

REMF33

p.s. I am not expecting anyone to do a mathematical calculation for me. Just wondered if anyone had set up a similar system for a similarish space, and if so what they do.

JennyJ

200l for 10 days gives you 20l per day in the worst case (if there's no rain to top up the butts while you're away). Is the 180ml per hour per dripper, and how many drippers do you have on each system? You could work out how long it would take to deliver 20l and maybe divide that into two sessions morning and evening each day.

KT53

I use a mains fed system so delivery rates are obviously very different, and mine is used for pots and baskets.  The drip feeds deliver 4 litres per hour and I have the system set for 7 minutes per day.  I change to twice a day in hot weather.  I will let you try to do any maths to match volumes.  7 minutes generally just has water starting to drip out of the baskets and pots as it turns off.

REMF33

Thank you both. I was wondering if 20l a day is actually too much. I had thought it was 180ml for the whole system rather than per drip outlet. I am not really au fait with exactly how these things work. I can detach the feeder pipe from the pipe with holes and leave for a set time to see how much I get. Would be sensible...!!! Will go and do it right now, in fact!

REMF33

Ha having a look at one of the raised beds, there is a high probablity that the water butt is not sufficiently elevated. Ah well. We shall see. I've had a good crop if all fails...

JennyJ

If the drainage is OK in the beds you can't really overwater. 180ml per hour for the whole system would only deliver around 4.3 l per day if you just left it running all the time, which doesn't seem like much to me.

Edit: 4.3 l is less than half a large watering can full.

REMF33

It doesn't sound much, does it...

JennyJ

If that's really how little it delivers I'd just leave it on and not bother with the timer.

JennyJ

My drip system is mains but with a pressure reducing valve, and it's for plants in containers so the situation is different to yours. I have it set for 5 minutes twice a day unless the weather turns hot and/or windy in which case plants need more water and I up it to 10 minutes. For the initial set up I started it running and timed until water started coming out of the bottom of pots.

REMF33

Alas that means buying new connectors for the tap. Sigh. No time, now. One should never leave these things till the last minute! I can set it up to run for half an hour every hour. Will probably be enough if the current weather continues. Better than nothing, anyway...