Inverted Siphon

[SiPaul]

We discovered a type of check valve on the downstream end of an inverted siphon. Does anyone know what this may be used for. There is a relief valve near the check valve ( in the low section of the siphon - bottom of the 'U'). Perhaps has something to do with this. Siphon was constructed around 1930.

 

[RWF7437]

The check valve is probably used to prevent bachkflow through the siphon. The other valve may be used to permit draining the siphon completly at times when repairs are necessary.

Just a guess.