Automatic Solar Powered Greenhouse Watering System





Introduction: Automatic Solar Powered Greenhouse Watering System

It used to annoy me that my tomatoes would split due to a lack of water while i was at work, so i decided to build an automatic watering system so this could not happen! i wanted it to be solar powered so that i did not have to run cables from the house to the green house. the system has been working now for 2 summers (coming up for the third!) so its been proven. so here is my instructable of it! this is my first instructable so i hope its clear and detailed enough, if you have any questions or queries just let me know!

just thought I should add that I went on holiday for 2 weeks last year and the greenhouse looked after itself with no problems! apart from the weeds etc of course!

Step 1: Aquiring All the Parts

the first thing to do is to get all the parts you need, you will need the following components:

a water butt for the greenhouse (i have assumed you already have one)

12v Bilge pump (around £10) (if you didnt want to use a pump you could mount a water butt high up and use gravity to feed the system)

12v solenoid valve (£7)

12v programmable timer (£6.50)

12v solar panel (i used a 15w panel, it cost around £30)

12v solar charge controller (£6.60) (not essential but recommended)

12v battery (£10 each for a 7ah) (1 should be fine, however i used 2)

pipe work, fittings, hose clips, cable etc.

Step 2: Building the Pump Side

connect a length of hose to the pump and run it to the greenhouse and attach the solenoid valve to the end.after this, decide where you want the water to go and lay some perforated soaker hose, or simply cut/drill some small holes in some ordinary hose.

once you have done this attach both ends of the perforated hose to a t-piece pipe fitting and then attach the solenoid valve to the t-piece as well. you do need a solenoid valve really to ensure the system does not siphon from the water butt once the cycle has finished. another note, from my experience it is best to place the t-piece somewhere around the middle of the bed to ensure an even flow of water in each direction.

i think it is better to lay the hose around whatever you wish to grow and then lay more soil on top to ensure it does not evaporate during the day.

Step 3: Building the Electrical Side

first you need somewhere to store the battery/batteries (i think you could get away with just one, but i decided to use 2 as i added a small hose to my system as well). i made a small box out of some old pallets to keep the batteries dry, and to store them outside. i built a small roof which allows ventilation but stops rain from entering the enclosure.

then run a cable from the battery enclosure to wherever you wish to keep the electronics inside the greenhouse, i had an old electrical enclosure kicking around but you could use anything really, it doesn't even need to be enclosed it could just be mounted on a piece of wood! run the cable from the battery to the solar charge controller and connect it as shown in the diagram. (a charge controller is optional really, but for the price it worth it as it will ensure your battery/batteries as kept healthy by not letting them get too flat and not over charging them).

now mount the solar panel somewhere in lots of sun, i attached mine to a pole and mounted it to the water butt. run a cable from the panel to the charge controller and attach it to the solar panel terminals.

then attach some cables to the 'load' terminals on the solar charger and fit them to the programmable timer to the power connections. and finally from the output side of the timer to the pump and the solenoid valve.

now everything is wired up!

my panel looks a huge mess as i used 2 timers i already had and made up a timing circuit, however if you buy a normal 12v programmable timer there will be much less wiring and it will be MUCH neater! also if i did it again i would use smaller pipe for the pump.

Step 4: Programming the System

OK, now everything is connected up all you have to do is let the battery/batteries charge for a while, the charge controller will not allow you to use too much of the battery helping to keep the battery healthy.

so in the mean time plant some tomatoes/chillies/whatever you want and put some soil over the pipes, at least an inch or two i would say!

so once there is enough charge in the battery you can program the timer. set it to whatever you wish, my system usually waters for about 1 - 3 minutes every 3 - 4 hours depending on how hot it is as i change the settings to suit. hopefully you should find that the soil may look very dry on the surface but scratch down a bit and it will be lovely and moist! i hope this works for you!

2 People Made This Project!


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19 Discussions

Hi i really want to make this. But i dont completely understand the hose setup. Is it possible you Can upload a hose plan diagram?


2 years ago


Do you know how far the pump will pump?

I was thinking of running a pipe around my garden and just using drippers/soakers at my fruit trees.

It's about 30m length though.

9 replies

The small diaphragm pumps should lift about 30 metres at about 60 psi. My place is about 30 metres above our creek and I use 2 pumps staggered one by the creek and one half way up connected to a holding tank .

The bottom pump runs 20mins on 10mins off filling the tank halfway up and the pump on the tank just runs using a level switch till it's empty. The bottom pump lifts about 20 metres and the next one only lifts about 10 metres.

They have a 80 watt panel charging a 15 amp/hour for each pump

Hi with pumps its not so much about length its about hight in the case of the one in the picture thats is 13ft up. It should be ok for drippers and soakers. As I use this system to water my whole allotment with sprayers overhead like Errol. As long as the head tank is above the soakers- drivers you might not need the pump.

Any restriction in the pipe increases pressure but also reduces flow, If you then increase the size of the pipe you decrese presure as well. Do not use valves that constrict pipe diameter.

Thanks Richard, i tested the pump running ¾" up the garden to ½" back down the garden and had good flow at the end.
My only concern is that when all the drippers are in place the pump wont provide the pressure to drip as its centrifugal and will just sit there spinning?

hi, I have changed my pump since I wrote this, I now use a 12v diaphragm pump, it uses more power, however because it can maintain a much higher pressure it does not need to run as long. perhaps have a look into one? I got mine from Amazon, I still use a solenoid valve however, as my diaphragm pump has a built in pressure switch. you do need a very good filter on the feed lime however, diaphragm pumps are not as robust at handling debris as a small centrifugal.


Thanks for your help Ross My watering system works thanks to you.

Will post some pictures soon

that's good to hear, it's nice to know my instuctable was useful!


hi Ross, thanks.

I like the bilge pump idea for the butt due to the debris it will suck in.

I was going to put a 3/4" filter after it before the rest of the system to stop the muck getting down the line.

I've since found my water px gauge so will do a measurement and see what the pump can put out at the end of the run. Might determine what emitters I have to use.

I forgot to add, a diaphragm pump should illuminate and concerns with siphoning as well if you choose not to use a valve. (I have a hose pipe connected to my system, hence the requirement for a pressure switch in the pump).


If the pump dose work you'd like. You could pump water into a smaler elevated header tank, You could then gravity feed your drippers. You would then use a float valve in the header tank to operate the pump this would minimise run time of the pump.

I made this but with a few different items. I have replaced the pump with a small cheap high pressure pump and I do not use a solenoid the panel and the battery and timer are the same as the timer is quite capable of switching the pump. But using mist sprayers overhead and the high pressure pump are controlled by the timer. My system has been in daily use for nearly 15 years still using the same pump but have replaced the panels with a more efficient one and replace the battery once but I am using a German Kemo regulator as I have blown a few batteries using the cheap regulators

I made this it works well but the solenoid valve was really unreliable and I found it redused flow.
So instead I have drilled a very small hole in pipe after pump inside water tank above water level this stops siphoning effect.

1 reply

I did think a while back that if you were to have some sort of large funnel, say a coke bottle or large mild bottle with the bottom cut odd you could get away with not having the solenoid valve and lump water into the bottle like a large funnel attached to the watering pipes. I think that would minimise the run time of the pump too, allowing for less wasted energy and higher efficiency. that's for the modification.

Does the 12v timer always have to be powered to remember your program, or does it have an internal backup? I assume that the charge controller would sometimes cut off power to the timer if the battery runs too low. Are you aware of any timers which would be able to run more than one selenoid?

Thanks for the instructable.

Would you mind if I asked where you got the parts? I've been scouring the internet, but its hard to find a single place with all those parts, let alone those prices

1 reply

I got them from a well known online auction site! I dont know if I'm allowed to mention the name here but I'm sure you can guess! let me know If you still cant find them!

I had to look up "water butt" to make sure I understood. For those who aren't as British as the author, its a water tank or rain barrel.