Introduction: Hydoponic Garden - Gravity Feed

About: Just your average non engineer in beautiful New Zealand, solving my seemingly unique problems because I cant find any one else that has.
Join Instructables ( Free) and you can view this instructable on one page.

What are hydroponics?

Well quite simply, this is a method of growing plants with out soil, the plants roots are in direct contact with the nutrient solution. (nutrient minerals dissolved in water)

At their essential basic hydroponic systems are just another method by which to grow plants, but unlike the soil out doors, this method allows you to control and maximise the requirements of life in order to maximise end result.

How you maximise the conditions and requirements of the plants (food, pest and disease control) dictates whether you plants are truely organic or not. For the purpose of this instructable (and any thing I have my hands in !) it will be totally organic!

Step 1: Outline - My Passive Gravity Fed System

This instructable defines a system of hydroponics that is gravity feed, and provided you keep the nutrient tanks full, you only need to monitor plant health, occasionally maintain the system and chomp the end product. It is based in a small glass house, but has been run successfully inside on a window sill and in a conservatory also.

All references to "fig...." refer to the individual photos on below each page(each is labelled in the yellow squares)

In order for a plant to grow ( just like us..) it has 5 basic needs;
a.) Water supply (we supply)
b.) Food supply ( dissolved nutrient solution)
c) Light for photosynthesis ( Mr sun)
d) Temperature management (seasons + extension being in glass house)
e) Gas exchange ( Mrs nature)

.All instructions are based on my materials locally available - you will need to adapt them to yours.

You will need;

- Rectangle section hydroponic tray tube with end caps ( you can get it pre drilled too)
-(or standard guttering with end caps)
-Rubber grommets to suit tubing used 13mm & 4mm
- a grommet, and tap to match the size of pipe you wish to use for the drain pipe( 30cm of pipe) (hardware - irrigation supplies)(the pipe i use being 13mm irrigation hose)
- '''Autopot Smart valve Mk 11''' ( thanks to: Clive who read this instructable and found this far more reasonable supplier of smart valves!)
- 4mm tubing (Bunnings hardware irrigation supplies)
- 4mm tap (Bunnings hardware irrigation supplies or aquarium shop)
- 20 Lt plastic Jerry can
- Materials and construction tools to make a light prove box over Jerry (timber, screws, saw, drill, screwdriver in my case)
- Nutrient concentrate + tap I buy mine in 5 litre containers.(fit with a tap and decant in to one litre bottles for ease of us.)
- Hydroponic tray tube (100 x 75) you can also get tube tray with holes ready cut or standard house gutter.
- Plastic gutter PVC solvent cement
- File
-Hack saw / power saw
- Drill press ( ideal) or power drill
- Drill bits
- Drill saw (or method for drilling out circles of plastic)
- Inner tube band
- Gib board plastic corner lengths
- Self taping screws - four per tray
- Builders long level
- EC meter(Conductivity/TDS)
-Wooden wedges - 30 - 60 degree ( 4x per tray)
- Growing media - expanded clay balls
- Weight (quarter a brick )

Step 2: Autopot Smart Valve - the Core of the System

The core

The core of my system is a very tricky device that I discovered while living in Australia, called the Autopot SmartValve MKII

How it works:
The key thing about this valve that makes it so darn annoying (wish I could think of a way to do the same thing as I have to buy them from overseas currently) is that it first: meters the amount of nutrient solution to correct level ( it doesn't flood the plant roots constantly)

and second: When the plants have sucked up that nutrient solution, it keeps the roots dry for a period to enable the roots to breath, ( yes plants breath through their roots too) before the altered internal pressure of the device allows a new wash of nutrient solution to bathe the roots.

Step 3: Water Supply

Water Supply

Plumbing the plastic Jerry can

Step a
Fasten the plastic Jerry can (fig. 03) up side down securely and drill the correct hole for your nutrient tube grommet (fig. 04) (4mm tube in my case) hole

>> critical note- experiment with your grommet holes before you drill your container - some have the correct size hole dimensions marked on them, other wise you might end up with a whole to big that leaks. The grommet spreads when the tubing is pushed in to it but the hole <<

Step b
Push the 4mm supply tubing about a cm in to the base so that sediments and muck dont get in the line. (fig 05)

Step c
Cut two wooden blocks to support the Jerry can high enough so that the tube exiting the base is not squashed, and can naturally curve down to the tray tube. If you don't have the room for this you can use 4mm elbows. etc.

Step d
Position the Jerry can as high as possible above where the plants are going to grow, there must be a natural fall for gravity to supply the auto valve and the plants.(fig.06)

Step e
Construct some form of box and lid cover to isolate the Jerry cans from sunlight (algae love nutrient solution also!)(fig.29) see lid back in fig.06

Step f
Place a 4mm tap in the supply tubing at a location prior to the glass house below the Jerry can.(fig.07)

Step g
Drill a 5mm hole in the glass house frame and pass nutrient supply hose through from in side the glass house ( keep the roll in tact) - connect that end to the tap - put the roll aside for now (fig.22)

Step 4: Plant Pots

I used clear plastic disposable drinking cups for my plant pots.

>> improvement = constant diameter small tubes pots - the cups I use are tapered and you need to work out how far in they sit in order to cut the holes)<<

Step a)
Place a piece of wood inside the cup to support the plastic to prevent it cracking, and secure in vice.
Step b)
Use ideally a drill press (or a drill ) and drill a 8-10mm hole in the centre of the base, and 3 in the lower side above the base.( this may take trial and error so make sure you buy a good number - they crack easily) (fig.08)

Essentially you can use any small pot for this purpose so long as it has holes in the base as described. Plants in hydro set ups dont need large root areas as the food is right at their front door.

Step 5: Plant Trays

Plant Tray tubes

I use rectangular section hydroponic tube (100 x 75 ) but before this I used standard plastic house hold guttering / spouting.

Step a)
First cut your tube to size to fit your space / number of plants -( the most I have grown with one valve has been 1.5m /10 plants) this is best done with a table saw or band saw for a nice straight cut, other wise use a hack saw.

Step b)
File the cut edge nice and tidy, apply the appropriate glue and press the end caps on and leave to dry.(fig.09)

Step c)
Take your smart valve complete with cover and mark out its size + small allowance so that it will fit with ease in to the tube and sit on the base. Using a jig saw or hand saw, now cut the marked flap out beginning careful not to cut closer than 5mm to the sides or end flap - file the cute edges and try valve and cover for fit.(fig.10)

Step d)
Turn the tray tube over and at the opposite end to the valve location, mark a centre for a drain hole - to match the grommets for the diameter of drain tube you are going to use ( i have used garden irrigation pipe at both 13mm or 4mm.

There are two ways to control the flow of water from a drain tube - the best being to place a tap it, in this illustration i have placed the tap first then connected the tube but in hindsight it would be easier to insert the drain tube in to the grommet and then place the tap some where else in the drain tube.

if you are using flexiable drain tube like the 4mm type, then instead of a tap you can just loop it around above the tray tube height, bend the end back on its self and tie it closed like that.

Step e)
Secure the tray tube in a vice, and hold your choice of pots up against the end cap to calculate which measurement of the cup is level with the top of the Tray tube. (mine are tapered)
Mark out the diameters on the top surface of the tube with a centre mark.
( I found it was best to alternate left and right - see fig.12)

Step f)
Set up your hole saw to cut out the plastic circles

>> critical comment - through a combination of errors here ( the drill on my hole saw was bent, I didnt drill pilot holes, and my hands were in the wrong place I managed to interrupt my drilling to visit the doctors ( fig. 13) I was lucky !<<<<)

Also be sure that the standard pilot drill bit on the hole saw doesnt reach the bottom of the tube - you dont need a hole below!

My recommendation is you use the hole saw attached to a drill press with your fingers well away, if you dont have a drill press, then first drill a pilot hole in each centre,
when it comes to cutting the circles out of the tube.

Step g)
File the cute edges.

Step h)
Measure down the centre of the tube top approx. 100 - 150mm and mark a centre, - drill one 4mm hole in the top of the tube. This is for the nutrient tube to enter and pass back to the valve.(fig.23)

step i)
place the smart valve in place, feed the inlet tube through this hole and then back inside along the base of the tube tray to the valve and connect.

Step 6: Plant Tray Tube Placement

Tray layout

Step a)
I used lengths of gib board plastic corners(fig.14) to act as tray supports, each length cut to the width of the glass house so that the ends could then be screwed directly in to the frame to make it secure. On later versions I didnt screw them to the frame but placed inner tube retainers over the ends so they cant move apart.(fig.14a)

Place the supports in position, place the tray in the supports, and pull then together snugly.

Step b)
Insert the drain grommet and drain tube, so it projects about a 1 cm into the tray from the bottom - using cutters or a sharp knife cut some slits in top of the tube down to the base of the tray to allow all water to escape when tap opened(fig.11)

Step c)
Take the length of nutrient hose running from the tank tap (and roll) and measure out sufficient hose to make a nice gentle fall to the 4mm hole in the top of the tray tube, and then on inside the tray tube to the connection nipple on the valve. Cut the roll off, and attached to that end to the valve, tighten.(fig.15)

>> you may need to pre load the tubing with a twist or two inside the tray, so that when connected to the valve it doesnt alter the valves position flat on the base.<<

Step d)
Place the builders level (fig.20)across the full length of the tray and alter the lay using the wooden wedges placed under first one end ( both if required) so that the base of the tube is level.(fig.21)
>> Critical comment - this is crucial other wise the plants will not get water evenly <<

Step e)
Fill the Jerry can with water, open the tap and lift the valve out so that you can open the both floats and ensure water is running freely. Close all floats, put the valve back in place, place its cover on top and a weight on top of the cover.
Let the water run and it should stop at about 1 inch full video 1

Top up the Jerry can.

Step 7: Growing Media

Growing media

In this system, like plants growing in soil, the plants require a growing media, clearly soil is not the best option given its inability to breath in water.

I use expanded clay (balls)(fig. 24) a common hydroponic medium that allows good root ventilation, doesn't break down fast, and doesnt grow algae etc.,(avoid perlite, pumice other mediums as good as they are, they also grow algae on them )

Step 8: Plants for Your Systems


There are two ways to obtain plants to grow in your hydroponic system.

The easiest

Step a)
Go to your local plant shop and buy seedling plants of the type that you want to grow in potting mix.

Step b)
Get them home and tip them out of their pots in the shade, then using a running hose, gently spray the soil from the roots - DONT use your fingers as you will destroy delicate root hairs with ease.(fig. 16)

Step c)
When they root bundle is clean, suspend the plant in the centre of the cups (fig. 17) you prepared earlier, so that the roots form a coil on the base. (or come within an inch of the cup bottom)

Step d)
Now run clay balls in around the roots, (fig.18) giving the pot a gentle tap on the surface you are working on every now and again to firm down the balls. Fill to the top of the cup with balls.(fig.19)

Step e)
Using the hose running slowly - run water through the cups until all the clay balls are wet, and place in position in the hydropoinc tray tubes before the clay balls dry. (fig.19a)

Step 9: Plants for Your Systems Cont.

Self grown plants

The second method is to grow the plants from seed in a water only containing tray (see later about nutrient requirement) -

Step a)
Take a tray tube and cut out the centre as shown in fig.26 Place a smart value it using the same set up technique.

Step b)
Place pots filled with clay balls in as shown also in fig.26, putting the seeds under the last layer and a halve of balls.

Step c)
Wet the balls as you do in the first method and place in the water only tray

Step d)
Once the seedlings have produced all their first leaves, to the stage you would normally plant out - re pot in to clay balls as described above.(fig.30a)

Step 10: Nutrients


Mixing nutrient solutions is possible with out any special gear, I do however recommend purchasing and EC ( electro conductivity) meter,(27a) while they will appear expensive to start, they can be very mighty useful when it comes to calculating just how much concentrate is required to make up the optimum EC for a plant type. Additionally they are very good for defining which alterations to make to the fluid in the tray tubes, during for example hot days, and other enviromental changes.

While you can get a basic cheap EC meter, I recommend you splash out and get a waterproof combo meter, If you are seriously in to they idea of hydroponics, my combo measures EC, pH and temperature.

The best place to figure out the nutrient requirements of your plants is to goggle EC values (depending on your metre these are measured in cF or ppm). Each plant has its likes and dislikes which can make all the difference to how it grows or fruits.

The other difference to understand is that plants that are either growing vegetative structures ( i.e. leaves ands stems ) and those that now have flower buds or are ultimately going to produce fruit have different nutrients requirements.

There is plenty on this subject on the Internet, but lets keep it simple with regards to nutrients;
a) Seedlings - I use water only , then follow the nutrient recommendations of my supplier with a nutrient designed to promote green growth.(27b)
b) Mature plants - are up to full strength of the same growth promoting nutrient.
c) Mature plants that begin to flower ( and I am interested in the seeds, or fruit that transpire) I switch to a nutrient solution that promotes flowering and fruit production.(27c)

The flowering nutrient does continue to support green growth - but then I use and all in one concentrate. - ask at your local hydroponics store.

Mixing the nutrients

Step a)
First you need to shake your premix concentrate bottle well, ( you can see in fig.27d how it separates after only a short time)

Step b)
Pour in to a cup and before it can settle, use a disposable plastic syringe (27e)(60ml) to suck up the required amount (this is where an EC meter is handy you can easily calculate how much this is required) and add it to the plastic Jerry can which is full of water.

Step c)
If you are mixing the nutrients in a separate container ( ideal while you are learning) then put the cap on and thoughly shake. If you are mixing the water supply containers then take a length of garden hose and blow big bubbles(fig.28) in the water supply Jerry can.

Step d)
Using the EC meter - check the EC reading to be within the desired range - adding nutrient or water to achieve the correct level. ( it can pay to mix in another container until you get the hang of this)

Step e)
Log the plant type, the nutrients type, ( grow or bloom) amount of concentrate required, final EC etc. This means as you get more practiced you will not have to work it all out each time.

The only time I have had to act on nutrient levels was during high temperatures inside the growing area ( i.e. when living in Australia and the temp went above 28 Degrees Centigrade - water added directly to the tray tube. With out an EC meter one could certainly work it out but you would need a fine eye for observing plant health.

Now sit back and watch it grow....

Step 11: Maintenance

The float valves;
these can become blocked, if you have a look at them you will see that the water passes through a pin hole size so any particles coming from your tank will block this eventually.

to fix this - if you find that the tray is inexplicable dry, or hopefully before that occurs, take the brick over the cover off, remove the cover, lift out the valve and let the floats fall away to reveal the pin hole. if its blocked disconnect the valve from the inlet tubing and either blow or use a can of compressed air to blow the obstruction back out the inlet.

This not such a problem if you insert inline filters in to the inlet lines - not something I have done to date. if you use filters then of course you will need to periodically clean then out as well.

Plastic Jerry cans
nutrient rich water, will grow algae if sunlight can get to it and this of course clogs the system, so the prevention is much easier then the cure, but if some grows eventually you will need to clean the tanks.
1) turn off the outlet,
2) disconnect the outlet tubing the other side of the tank tap, so the tube and tap is still connected to the tank.
3) fill the tank with fresh water, and add bleach at the correct concentration and let it sit
4) once the algae has disappeared - it seems to go clear when dead, then empty the tank on some weeds some place, and flush with fresh water - you don't want any bleach in there when you reconnect it.

The Tube trays;
Just like the plastic jerry cans, if sunlight gets to the nutrient water you will get algal growth, while this doesn't clog the system it does use nutrients to grow and can also make for a foul mess in the root balls.
1)when algae has built up in the tube tray, remove all the plants to a bucket containing fresh water
2) place a bucket under the drain hole and empty the tube tray ( or attach a hose knozzle to the drain pipe and pipe the water out to the garden
3) turn the drain pipe tap off - refill the tube tray with clean water from the hose and add bleach as you did for the tanks, let it soak, then empty ( on to the weed patch this time) and flush several times using the same procedure.
4) pop the plants back in - make sure you have turned off the drain tube, and open the float value tap
5) i find the black plastic bag plant pots, which are known here in New Zealand as "PB's" are the best to cover unused holes, and the float valve, and put a weight on top of them, or use a squre of hydroponic black plastic ( thicker than normal black plastic)