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Cannabis Fact Contributed by: Lilly Leaf
This Fact entry offers a way to make a contraption that can
maintain the water level in your hydro hydroponic tank or
humidity cup. It is gravity powered and made from stuff
you can get at your local home maintenance store. There
are no moving parts other than water. I have built this
and it does work. Sorry, I do not have a digicam to
submit pictures.
I have been using this for the last 3 months to keep a
constant level in my humidity water within the grow room.
It works like a champ, keeping the level to within 1/16
inch of where I set it at all times. I used to fill the
cup every day, now I just replace the water bottle when
it is almost empty. I found that I was using about 2
liters per week during the winter while in vegetative mode (150W
HPS). Now that spring is here and ambient humidity has
risen, I have entered the flowering stage and water
consumption has slowed to about 2 liters every 3
weeks.
For those doing hydroponics, this is an alternative
methodology to maintain your hydroponic tank level if you go on
vacation. Past ways I have seen involve float switches
or valves. This technique may remove some of that
complexity for people who don't have easy access to those
items.
The technique is scalable. I have used it with 2 liter
soda bottles, but you can easily use a 5 gallon carboy
for holding the extra water. The only key requirements
are that the bottle holding extra water can be totally
sealed against any atmospheric air leaking in around the
edges and it must have walls that are stiff enough to
withstand a bit of negative pressure. The pressure comes
from the column of water and is equal to about 1/2 psi
for every 14 inches of height difference between the
bottle and the hydroponic tank top. A 2 liter soda bottle can
handle about 2 feet of difference (1 psi). A carboy has
thicker walls and can be mounted much higher. Sorry,
plastic bags of water won't work.
Construction Information
Here is a diagram that explains how to build the
contraption.
To seal the tubing as it enters and exits the soda bottle,
I use a material called Goop. This is a plastic paste that
hardens after solvents evaporate from it. You can get it at
Home Depot for $5 per tube. One tube will do dozens of
tubing closures. There are many other alternatives to this,
so pick the one that is right for you.
Most of the tubing is 1/4 inch black vinyl tubing found in
the drip irrigation section of your home improvement store.
It is about $5 for 100 feet. The larger diameter tubing can
be found in the same store in the plumbing
department.
I had trouble with getting the large 1/2 inch diameter
tubing to mate with the small stuff until I figured out
that you can buy a few inches of intermediate tubing to
join the largest size to the smallest size. I found that
1/4" OD (outside diameter) will fit snuggly into 3/8" OD,
3/8" OD will fit into 1/2" OD, and 1/2" OD will fit into
5/8" OD. I recommend using about 2 inches for each of the
intermediate tubing sizes. If possible, they should overlap
each other to add rigid strength to the entire tubing. Use
water or spit to lubricate each piece of intermediate
tubing when connecting and then push them on tight! This
will be your biggest source of air leak problems if they do
not seal against each other. If you have still have trouble
getting all the tubing to have an air tight seal, apply a
thin layer of Goop or other sealant to the tubing ends
before mating them.
You will need at least 6 inches of vertical height for the
5/8" OD vinyl tubing, more is better. This size is
elevated because it has 1/2" ID (inside diameter). 1/2" ID
is the smallest size tubing I could find that would
reliably let surface tension break when the bottom of the
air hose is exposed to the atmosphere.
When working with some of the larger diameter vinyl tubing
sizes, you may find that it wants to curl or flatten. This
is because the tubing is shipped to the store in rolls and
was curled and flattened during shipping. To fix this, dip
the tubing in very hot water. I boil water on the stove and
then put it into a shallow bread pan to let me work. When
the tubing is heated in this manner, it will relax and
become very pliable. Remove the tubing from the water and
lay it down straight while cooling. Use a small weight
(sdung wood, shoe, hammer) to hold it in place for about 15
minutes. Most or all of the curl and flatness should be
gone. If you have trouble inserting intermediate tubing
inside the next piece, dip the pieces in hot water and then
fit them together. The tubing is much easier to work with
when it has been warmed. You can reheat the tubing as many
times as you need to in order for it to behave.
Make sure you pay attention to where the ends of the tubing
are inside the sealed bottle and hydroponic tank. The water line
must extend to the bottom of the sealed bottle and
be under water in the hydroponic tank, the air line must
be short enough inside the sealed bottle to be above the
water in it. Failure to do so will result in a system that
won't work.
Operating Information
To use the system, Stick the water line into the hydroponic tank
you wish to maintain. Attach the air line to the side of
the hydroponic tank so that the bottom is right at the water
level you wish to maintain. I have found that keeping the
air line at the right level is the most difficult part of
operating this. I ended up putting a piece of soft copper
1/4" tubing on the end of my water line and then using
small diameter wire to attach the air line to the copper
tubing. The copper has enough weight and stiffness to sit
in my humidity cup without moving around. You will have to
determine the best methodology for your setup. If you come up
with good ideas, please post them in this thread for others
to use.
To begin using the system, fill the bottle with water and
then seal it. With 2 liter soda bottles, I just screw the
lid on tight and the tubing Sticks out of the top of the
lid. Now, you need to prime the tubing with water. You can
use one of two ways:
- If the sealed bottle has soft sides like 2 liter soda
bottles, just use your finger to plug the exposed end of
the air line and gently squeeze the bottle. Keep
squeezing until air stops bubbling out of the end of the
water line. Remove your finger from the air line and
gently pop the bottle back into shape if you have dented
it.
- If you use sealed bottle with solid sides, put the
end of the water line in your hydroponic tank and then gently
blow into the end of the air line until bubbling stops.
This requires you to figure out how to attach and remove
the air line during the priming process and may be a bit
difficult. Think about how you are going to do this
before starting.
Problem Solving
If you find water keeps dribbling out past the cutoff
point, you have an air leak into the sealed bottle or the
bottle is too high above the hydroponic tank. To find air leaks,
check to make sure the lid on the bottle is screwed on
tight. Make sure you used enough sealant where each tube
enters the bottle. If you have different sized tubing
fitted together to change sizes for the open end of the air
line, check to make sure you aren't getting air leaks
through the gaps where tubing fits. Air leaks can be a pain
to find and I have had most trouble with it coming in
through the different sized tubing I use to adapt the 1/4
inch air line to the larger diameter at the open end.
You will know if the bottle is too high above the hydroponic tank
because the sides of the bottle will start to collapse.
This happens if using soft sided soda bottles like I have.
To fix it, you must reduce the height difference between
the sealed bottle and the top of the hydroponic tank.
If air gets into the sealed bottle or the air line is not
properly secured and gets exposed to the atmosphere, the
entire contents of the sealed bottle will leak out. You
should be prepared for this by making sure you have
hydroponic tank large enough to hold the entire contents of the
sealed bottle or use a catch basin (hydroponic tank in a bucket)
around the outside of your hydroponic tank. I left a system to
eat dinner and accidentally let the air line flip out of
the hydroponic tank. The entire contents of the sealed bottle
where all over the floor when I got back.
How it works
This system is really a siphon. Like all siphons, it is
powered by gravity. The sealed bottle and air line are the
secret to keeping the siphon from spilling all its water at
once. Air must enter the sealed bottle to displace the
water as it leaves. The only place air can come from is the
air line. When the hydroponic tank level reaches a point where
the air line entrance is submerged, no more air can enter
the sealed bottle. If you use clear tubing for the air
line, you will actually see the water climb up inside it
until the water level reaches the same height as the water
level in the sealed bottle.
When the hydroponic tank level drops, an air gap opens up between
the hydroponic tank surface and the air line. The air line is
full of water, but the large diameter tubing prevents the
water surface tension from holding the water in place. The
water that was sucked up into the air line runs back into
the hydroponic tank and air is again allowed inside the sealed
bottle. When the air line entrance is again submerged, the
cycle is complete.
If you use a hydroponic tank with a large surface area, be
prepared for the filling cycle to suck relatively large
amounts of water from the sealed bottle. This is because
the amount of water required to bring the hydroponic tank back up
to level is relatively large compared to what the sealed
bottle contains. In this case, you need to use more than
one sealed bottle or a larger bottle.
Conclusion
I have found this technique works well and can be used
instead of a float valve. Besides the materials, the only
thing it requires is to ensure the sealed bottle is
always higher than the water level in your hydroponic tank. If
you need more capacity than one bottle will hold, I have
done this with up to seven sealed bottles that feed into
each other. This gives me fourteen liters of storage. You
can extend it to as many bottles as you need for whatever
capacity you require.
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