Aspirator (A bomb) problems on dual siphonic pan

23 Apr 2007
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United Kingdom
I've fitted a new aspirator (syvac) and dudley turbo 44 syphon to the cistern of a dual siphonic pan as the pan wasn't syphoning.

The pan now syphons when the cistern's flushed, but at the end of the flush the depth of seal is only ~0,5" rather than the original 3 or 4 inches. Originally, at the tail end of the flush the depth of seal would rise back up. Now this isn't happening.

The way I understand how the aspirator works is it draws air from the void between the two traps to start the syphon action. Then as the cistern is close to empty it introduces air back into the void breaking the siphonic action.

The problem I've got is the siphonic action in the pan is only broken when the water level in the pan drops below the seal which is right at the tail end of the flush, so there isn't any water left in the flush to bring the seal back up to level. I'm thinking the aspirator isn't introducing air back into the void enough to stop the syphon action a bit earlier.

I've given Dudley technical a call but no joy yet. All I can come up with is the aspirator isn't a tight seal into the base of the dudley turbo. Its somewhat of a loose push fit. (its not like the airex type that screw onto the syphon base) I'll wrap some ptfe tape round it see if that makes a difference.

I did have to trim the aspirator tube as it was hitting the bottom of the hole leading to the void when first coupling the cistern to the pan. I'm wondering if I need to trim it a bit more so that it pokes out just a few mm below the bottom of the bomb washer when the cisterns coupled to the pan. Currently it pokes out ~1" beyond the bottom of the bomb washer and into the hole leading to the void.
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