Dudley S9 Hi-Flo 7.5  inch Siphon 317963 Duoflush WRAS Approved 

PRODUCT DETAILS:

• The S9 Hi-Flo provides a reliable toilet syphon replacement for most high level and low level application
• 6/7/9 Litre One Piece Syphon, suitable for high and low level use
• 38mm [1/5"] Outlet

CHOOSING THE CORRECT SIZE DUDLEY SYPHON

There are 3 sizes in the S9 Hi-Flo Syphon range.  You need to ensure you purchase the correct height otherwise you will not obtain optimal flush AND the syphon may not fit into your cistern (and stop the lid closing!). 

There are 2 ways to identify which size syphon you need:
1.  Installing a S9 Hi-Flo for the first time or replacing a different syphon with a S9 Hi-Flo:  To find the correct height of the required syphon for a cistern, measure the depth of the water level line, within the cistern, normally marked at the back of the cistern, and then add 1” or 25mm to this measurement.  This will give you the height of the required syphon. (Cisterns fitted before 2001, would have an original syphon in them that would be approx. 1 ½” or 40mm taller than the current requirements).
See the Dudley video here on how to measure the water line.

2.  If you have an existing S9 Hi-Flo and are confident you have the correct size syphon for your cistern then you can just measure the syphon to enable you to choose the correct syphon:  See photo 3 on this listing which shows dimensions.   Where it says 'HEIGHT' that is where you need to measure on your old Turbo 88 syphon to enable you to correctly purchase the correct size syphon.  Basically take the measurement from the bottom of the flange of the threaded tail (where the threaded part meets the moulded part that is almost in line with the oblong bulkier part of the syphon to the spillover point of the syphon (which is the bottom of the oblong bell part/moulded ridge on the domed cap at the top end of the syphon).  When choosing a syphon the height stated will be the height to the spillover point and not the overall height of the syphon. (i.e. an 8” syphon would be 8” to the spill over, whereas the overall height would be 10”) Below we have listed the possible height sizes and which syphon size that aligns to: 

 SPARES: BE PREPARED

• Diaphragm - FTB475 here - Consider purchasing a diaphragm when purchasing this Syphon.  Diaphragms disintegrate and perish over time.  Have a spare one on hand to ensure optimum flushing.  

VIDEOS / TECHNICAL DOCUMENT LINKS:

• Dudley Data Sheet showing the standard dimensions of a S9 Hi-Flo here

QUESTIONS & ANSWERS:
Q1:   Does a toilet syphon have an in built internal overflow?
A1:   A syphon can be used as an internal overflow device, as long as the spillover point of the syphon is below any other external hole within the cistern body, normally the lever hole.

Q2:   How do I fit a toilet syphon to a close coupled toilet?
A2:   When fitting a syphon to a close coupled toilet, you need to ensure that the threaded tail of the syphon is trimmed back, to ensure that the syphon flush is not throttled back, giving you a poor flush. We recommend that the tail is trimmed back to 2-3mm from the back nut.

Q3:   How does the dual flush toilet syphon work?
A3:   The operation of the dual flush syphon, is to flush and release the lever to give you a full flush, and to flush and hold the lever down, to give you a reduced flush. By holding the lever down, this lifts up two washers (one small blue plastic and one small black rubber) that are located immediately below the metal C link. When these washers are lifted up, this allows air to enter the syphon and breaks the syphonic action, the water level in the cistern will drop to just below the top of the syphon body, therefore giving you a reduced flush

Q4:   How does the internal overflow on a toilet syphon work?
A4:   A syphon will internally overflow when the water level within the cistern reaches the spillover point. The water will trickle over the spillover point, and run down the downleg of the syphon, and into the toilet bowl.