Siphonic aspirators / poor flush action

[Harry Bloomfield]

OK - never heard of siphonic aspirators, until the recent post. We have two toilets, of exactly the same design, same flush tank, same fill valve ect.. Both have always had a poor flush - customary method, is to have a jug of water to hand, press the handle, and add the jug of water, as the flush gets under way.

Toilets bowls are both the same design, the upstairs one exits sideways via a plastic 90 deg adaptor, then rigid pipe through the wall. The downstairs one, discharges straight down, and under the concrete floor. The cistern is the usual low level, linked to the bowl via a flush pipe, with a 90 deg bend, to enter the rear of the bowl. In cistern, the siphon is a Dudley 88 dual flush, which sometimes works to give a short flush, if the handle is held down - mostly it doesn't.

The level in the bowl doesn't rise, doesn't fall, even during a flush. Our upstairs stack, is open vented, the downstairs one is unvented.

I fitted the Dudley 88's, as replacements for the earlier units, after one of the earlier units gave issues after many years of use. I have no idea what the earlier items were, but both systems gave poor results. Both cisterns refill to maximum capacity when flushed. So, what is/does a siphonic aspirator do? Should I be fitting one to my toilets?

 

[denso13]

They are for double trap syphonic pans only, not for normal ones.

 

[Hugh Jaleak]

Firstly, where/how the pan discharges is irrelevant, P and S trap pans were available, and all worked on the same principle. Single Trap siphonic pans were also available, although seem to have been less common.

Aspirators were fitted on double trap siphonic pans, ones I've seen/worked on were close coupled, so the Aspirator sat in the tail of the siphon, secured by a retaining nut, and the tail of the aspirator had to be carefully located into a small hole in pan, when the cistern was offered onto the pan, then the cistern gently lowered onto the pan, to ensure the domed washer on the aspirator tail made an airtight seal on it's seating. Wingnuts could then be tightened in sequence to affix cistern to pan.


Siphonic WC's were designed to be almost silent when flushing, usually there is some extra detail visible in the casting of the pan, which gives away the additional internal workings. Picture courtesy of Twyfords.