My final growbed almost ready, lately getting a bit difficult to get the 80 mm end cap. While waiting for it, decide to try using the outer strainer itself as a bell.
This strainer is the type that I use that extra end cap inverted to form a holder, as in this posting making it easier to try out various style for a strainer.
For trying out, this strainer I only made 2 row of holes instead the usual 4 or 5, this to ensure water level will be low. Siphon cut off will occur once it reaches the first top row of holes.
Above looking from top, without usual inner bell and below with the flat 110 mm UPVC endcap.
It works, and siphon cut off will be at the highest row of holes leaving almost slightly more than an inch of water. With just two row of holes I'm not sure how will it stand against root growth and clogging, normal it will be 4 rows minimum but this will makes water in growbed to be about 2.5 ~ 3 inches at siphon cut off.
Trying out on earlier growbed, remove the inner bell and capped the strainer. It work no problem but this strainer has 4 row of holes so water is higher.
This can be use if shortage of parts or to reduce cost of making one siphon, but it need to be tested against roots growth etc.