Note : Further design improvement of this siphon : Here
I had many feed back regarding the siphon design on usage of smaller funnel inlet to the stand pipe. My standard design make use of 50mm ~ 25mm reducer as illustrated below.
I decided to redo this valve with 40mm ~ 25mm reducer as shown below and see how it goes. Its still too early for me to say whether its working without problem but so far the result is positive.
With this reduction to the stand pipe inlet size it will then be possible to reduce the overall size of this valve and still maintain the same siphon muscle to the growbed.
During initial testing of this smaller size inlet, I found that it needs more inflow of water to create the siphon this in effect could reduce ranges this siphon will work. What I suspect is as you are nearing the stand pipe size in this case 25 mm more inflow will be needed to create a siphon.
Photo above is the standard siphon on the left with the reduced inlet on the right, both these siphon is identical in its size with only difference is the reducer used.
Photo below for the standard siphon from top, with water overflowing and down the 25 mm stand pipe.
Photo below is the 40mm inlet siphon, note that the bell and strainer pipe is still using the existing which is for the 50mm inlet siphon.
I will need to fabricate entirely new bell and strainer to ensure it is better matching the smaller inlet diameter.
I turn one of my growbed into a testing bed for the siphon, it work just fine. Proper size pipe needed for the bell, ideally the bell pipe should be about 70mm but this tube size is not available so I settle with 82mm sewage tube which is smaller in diameter than a 80 mm pvc water pipe.
More testing need to be done, I should make a siphon tester next. Doing test on growbed is just too risky for the plant.
The 82mm sewage tube I use cling wrap plastic to seal one end making the bell, I could not find an end cap for it.
I did a quick comparison test on the revised siphon on my home kit.
The setup is as follows;
- Water in flow is provided by 1 pump rated at 1100 litre/hour (actual in flow is less due to height)
- Siphon Bell diameter of 75 mm (internal)
What changes are the stand pipe size as follows;
- 50 ~ 25 mm reducer with stand pipe
- 40 ~ 25 mm reducer with stand pipe
- 25 mm stand pipe extender - straight stand pipe.
Photo above from left to right are; 50~25mm reducer, 40~25mm reducer, 25mm pipe extender and 75mm siphon bell (using cling wrap to make it air tight)
The test did was a simple siphon starting time using stop watch. The stop watch is started as soon as over flow is detected from the siphon outlet and stop when full flow occur. Time taken will be the siphon starting time at same water inflow for all the different setup.
Photo above is the full flow of the siphon.
BTW Siphon outlet can be like this with slight restriction if you choose not to use the elbow type.
Tabulated below are the results of this simple test, and it may change the way how I make my future siphon.
As you can see from the above, time taken for siphon to start reduce significantly from the bigger diameter to the smaller diameter pipe. It took 55 seconds to start a siphon for the stand pipe using 50~25mm reducer down to about 5 seconds it take for the straight stand pipe.
However on the 25mm straight stand pipe, siphon do not reset causing the dreaded equilibrium flow. The above short test clearly show the 40~25mm reducer siphon is the best option in this situation.
Above is the equilibrium flow, water continuously flowing out the growbed non stop causing the low water level phenomena. Apart from causing this, the straight stand pipe also has an almost silent down flow with minimal water disturbance or noise as compare to the stand pipe using the reducer as below.
I will do more test, to check which siphon will deplete the growbed water more and what effect does the outer bell size has on the siphon effectiveness.
I am changing the siphon sizes to make it more efficient and better reliability. However this is still to soon for me to make any concrete statement on the smaller size funnel usage.
It does looks good, so I am retrofitting one growbed with this size siphon.
No luck today, hardware store here don't stock 65mm PVC pipes and fittings. They say there is no demand for such size. Being an uncommon size I am reluctant to include it in my siphon part list.
Instead of getting the 65mm pipes I bought three 32 x 25 mm reducer to try out. Photo below show it along side the 40 x 25 mm reducer.
I am testing it now, so far so good no equilibrium flow. I am thinking of making my valve kit available for those that have difficulties in getting the correct size fittings to make their own. Since all 3 sizes will work with my standard valve size i.e the bell and strainer pipe.
I think why not include all three reducer in the kit, this way user can try out which one is best for their setup. It going to cost extra but not by much.
So if I homemade siphon kit as below and make it available worldwide will people want it ?
The kit will be build as below :
Include all these three reducer in the kit, it should very much cater for most people needs.
Updates : 29th May - Final
After a lot of testing, assessment on parts I found that the viable improvement on the siphon design is to reduce the funnel size by using the 40x25mm reducer without any other changes to the initial bell size.
This will allow user to use various sizes of reducers as shown above while maintaining commonality across the design of the 25mm size variant.
On variant that use 15mm or other size you just have to use reducer/adapter funnel size and bell size to suit your installation.
The principle concept and design of this design remains unchanged only slight alteration to its dimensions due to parts differences at different locations.
Updates : 30th August 2010
Siphon outlet for high water level is completed and can be view here the completed work. Simplified diagram as below.
This is a diagram of the revised siphon, material use are estimate base on industry stand PVC pipe available in the market here.
I need to check local hardware store this weekend to get all the sizes mentioned below.
There will be a limit to how small a siphon can be made to work with average size grow bed. One thing that we need to take into account is maintenance.
If the siphon is made too small then it might make it prone to clogging by roots growth and it could also be difficult to clear it of root growth due to limited access.
Additional note :
Due to non availability of the 65 mm pipe, all siphon dimension are the same on both the 50 mm and 40 mm reducer type. They can be use in same installation by just replacing the adapter part, I have use 40mm adapter for more than a few months without any problem.
