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Low rate automatic house plant watering system

I'm sure there is a technique, it just won't come to me.

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Colin Whittaker02/03/2019 10:03:32
98 forum posts
12 photos

The background. I live in Thailand. My kitchen is open along one side and has a tiled concrete floor that can handle getting wet. I have house plants in pots along the open wall of the kitchen.

I've just installed a reverse osmosis (RO) filter system to provide drinking water at my kitchen sink.These RO filters generate around three times as much water as they filter. This waste water is normally poured down the drain or, I could use it for house plant irrigation. Back of an envelope and bucket collections suggest I'll have around 5 litres per day to play with.

Trouble is the rate is <<1 l/min so adjustable chokes to distribute the flow to three or more pots will be unworkably sensitive.


Water to a header tank that flushes when full?

A cascade system that waters one pot and then triggers the water to the next and the next? How would that work?

Just fill a watering can and manually water the plants? Come on! I'm an engineer.

Thanks, Colin

Edited By Colin Whittaker on 02/03/2019 10:04:37

duncan webster02/03/2019 10:12:21
2168 forum posts
27 photos

My limited knowledge of gardening suggests that you're not supposed to water during the heat of the day, leave it till it cools off in the evening, so some kind of storage tank system is called for.

Bazyle02/03/2019 10:26:37
4656 forum posts
185 photos

Small oscillating engine used in reverse as a pump powered by a solar panel to lift it up to a header tank. Got to get some engineering in there somehow.

Chris Trice02/03/2019 10:26:45
1362 forum posts
9 photos

Car windscreen squirter motors supplied with water from a central water reservoir operated electrically either individually or in parallel or on timers.

Adam Mara02/03/2019 12:29:09
70 forum posts
4 photos

Gardening is my main love, and a lot of things I make on my lathe and mill are for my irrigation systems. There are various options, including drippers and sprinklers. In the greenhouse I tend to use trays with capillary matting in them, with a timer switching a solenoid valve to gravity feed water from a raised water butt. Pots are checked with a moisture meter, and the valve timing adjusted to suit.

AdrianR02/03/2019 12:38:38
272 forum posts
20 photos

Assuming you have some pressure available on the RO outlet, my crack pot design would be;

Mount an auto flushing urinal cistern several meters up, not a fancy electric one, just the old fashioned fills and flushes one. Fill it with the RO output.

Construct a small water turbine, attached to a bell, and connect to the flush output.

Below this mount a header tank that receives the flush.

From the header tank run normal drip irrigation.

As a cistern is about 5L capacity you will get a flush per day which should keep the plants happy.

The bell will give you that warm fuzzy feeling day or night that it is all working and your plants are getting watered.

A low tech alternative and politically correct green, would be to replace the cistern with one of those bamboo water features. The ones that fill a length of bamboo and when full tips over and empties. That could then empty into another length of bamboo which replaces the header tank. With a bit of ingenuity you could replace the drip feed with smaller diameter bamboo and reeds. You still get the audible operation indicator from the donk thump of the bamboo tipping.

Edited By AdrianR on 02/03/2019 12:40:26

Colin Whittaker02/03/2019 12:57:48
98 forum posts
12 photos

Guys, articulating the problem got grey cells working.

The solution I'm inclining towards is an automatic siphon (think men's urinal down the pub). Once I have a header tank full of water the siphon starts with enough pressure (around 2.5m height) to reach all of the plant pots.

The obvious temptation is to build it all from transparent plastic, but an opaque set up may be less of a time waster; it's 95% full and I'll have to wait while it triggers.

Now will a single stage siphon suffice or do I have to go multiple stages? siphon strip down

We seem to have a surfeit of Bromeliads and they're pretty tough so I'm not planning on any control to the humidity level of the coconut husk growing media.

Thanks all, Colin

Colin Whittaker02/03/2019 12:59:28
98 forum posts
12 photos

Adrian, So sorry. I posted before seeing your solution. Great minds etc.


Bazyle02/03/2019 19:00:09
4656 forum posts
185 photos

When the fill rate is slow autosyphons don't work. If you search hydroponics and automatic watering you will find some of the enthusiasts have gone to some lengths to invent systems that do work. One of the simplest a friend made some 30 years ago involves a tipping trough asymmetric profile, so that when it goes over the syphon gets the necessary sudden flow.

John Haine02/03/2019 20:51:50
2577 forum posts
133 photos

A perfect opportunity to add interest by making one of these:


duncan webster03/03/2019 00:31:01
2168 forum posts
27 photos

If you have the tipping trough thing why do you need a syphon? Just have it tip into a chamber which then has feeds to each plant pot.

It would be a lot more fun to have a little gauge 1 track along the wall above the plant pots, a small tipping trough tips into a jubilee skip type waggon, then the loco pulls it to a plant and another actuator tips the water into the plant pot. Small microprocessor controls the whole thing to make sure each plant gets its share. Over-engineered? definitely, fun? Oh Yes

Hopper03/03/2019 06:58:19
3651 forum posts
72 photos

You're in Thailand. Collect the water in a watering can and get the housemaid to water the plants.

Ed Dinning 103/03/2019 09:18:32
24 forum posts

Hi, opaque or black plastic watering pipes will stop anything growing in the low water flows and the heat.

A header tank or resevoir and then a peristaltic pump for low flow rates, through chokes if necessary to equalise flows.


Colin Whittaker03/03/2019 09:19:09
98 forum posts
12 photos

Bazyle, auto siphons at low rates is a concern. I just registered at PhysicsForums to have an excuse for posting the following, on low rate autosiphons. But I can well see myself resorting to a tipping trough if I can't get a siphon to work reliably.

Alan Jackson03/03/2019 10:28:04
164 forum posts
67 photos

Hi Colin

I spent many hours trying to make a plant watering system. I eventually made a system that used evaporation to instigate watering, which I patented, now long expired. I will try to upload some photos into an album, but will have to do it later when the slow internet I have is less busy.


Ian S C03/03/2019 10:40:26
7427 forum posts
230 photos

Do you have Mosquito problems, my niece in Townsville(Australia) got a water ornament for Christmas a few years ago, by the next morning there were mosquito larva in the water. Open water maybe not too good.

Ian S C

Alan Jackson03/03/2019 12:44:59
164 forum posts
67 photos

watering system.jpgHi Colin,

Here an evaporation controlled irrigation system. Wen the water in the top dish evaporates the water flows out then replenishes the tank for the next go.


distribution pipe.jpg

Neil Wyatt03/03/2019 17:10:56
16293 forum posts
681 photos
74 articles

Your biggest challenge is that the amount of water needed varies with temperature, humidity, light levels and the state of growth of the plants.

Something controlled by a simple in-soil sensor might work best .

The very simplest is to have the 'control plant' on a see-saw, when it dries out, it rises and operate a valve. You might need to change the balance as the plant grows.

Colin Whittaker04/03/2019 02:01:36
98 forum posts
12 photos

Ian S C,

In Singapore it's against the law to breed mosquitoes; not here in Phuket. Irrespective of my water features the neighbours will always have inadvertent water traps. So yes we have mosquitoes and when they begin to annoy then I light a mosquito coil. If you burn them inside something like this then it feels more atmospheric. No malaria in Phuket but there is Denque fever, touch wood, I've not been hit yet.


An adjustable see saw! I like it. Getting some hysteresis should be straightforward but I'm not sure how to realise a mechanically triggered valve. Could a crease in a hose close things reliably?

To all, Has anyone got any details on a multistage siphon where a baby siphon helps trigger a medium siphon that finally triggers a big siphon? It's always fun re-inventing the wheel but ...

Cheers, Colin

StephenS04/03/2019 03:31:30
31 forum posts

I have just found this site and have only had a very brief look at it, but it does look interesting.


May or may not be helpful, hope it is.


Edited By StephenS on 04/03/2019 03:32:05

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