Cistern Hints

The 2 most common problems with these, are either the plastic syphon lever breaks, or the ball valve will not completely stop the water flow, and the water goes out of the overflow pipe. If the lever cracks and breaks, it is a very easy matter to replace it. A new one, obtainable from most good DIY shops for less than a pound, should come with its own brass or plated screw. Just ensure you hook it properly into the “S” hook (should still be on the syphon pull-lever, the bit that gets pulled up), then with the flushing lever in its normal horizontal position, slide the lever onto the square section of the lever rod inside the cistern. When slid on level with the pull-up rod, screw it resonably tight, but not overtight, else the part may crack. NOTE: if replacing the complete lever and arm, IDEAL STANDARD take a non-standard(!) smaller threaded nylon fixing shaft (around 16mm), whereas most of the others are OK with a “universal” one, around 19mm.

Here below, is a picture of a syphon lever:


If the problem is not shutting of properly, this can be several things. Gradual Wear might mean that the red float and arm never presses hard enough onto the rubber diaphragm to shut off the water, so it gets too full, and continually exits from the overflow pipe.There is usually a nylon adjusting screw, near the top of the valve, where the float arm hinges. This can be screwed in a bit at a time, to get the water level correct. Don’t forget to tighten up the plastic lock-nut.

The red float-ball can also develop a crack, or leak, and if it gets water inside it, will not work efficiently as a float. If you hold the lever up, the ball can be unscrewed to inspect it, and ensure that no water is inside it. Most DIY and plumbing shops will stock these, at around £1.50, but SCREWFIX part 19902 is only 32p! I have to say this is rare though, I have NEVER had to replace one in any of my properties.

The diaphragm that is inside the valve, can develop a small hole, and leak. These can be replaced, but there are 2 or 3 different types and sizes. Scale or debris can build up on the diaphragm, but either way, you have to isolate the water inlet pipe, and unscrew the plastic ring-nut holding it. Clean it up and inspect the diaphragm for pin-holes. Re-assemble, and test. Note that older float valves will have a brass cylinder inside with a flat rubber disc in one end. You usually have to remove the brass cotter-pin and float arm, to get at this, it just slides out.The cylinder unscrews into 2 parts, releasing the rubber disc. Just replace and refit. If you have had to turn off ALL the cold water to do this, now is a good time to fit an isolating or service valve.

If I have to mess with an OLD float valve, I usually replace it with a TORBECK VALVE (Screwfix number D14716), as these are MUCH QUIETER than a standard ball valve, at just £3 more. Note that if your feed pipe comes in at the BOTTOM of the cistern, then you need a BOTTOM ENTRY BALL VALVE (stop giggling). Screwfix number is D19960. Take care that when you have got the float and rod clipped into the correct vertical position, the the “extra” positions sticking up above the valve, do not foul the cistern cover once replaced. If it does, it will NEVER shut off. Just cut off the unnecessary 2 or 3 inches of the plastic rod, with side-cutters, so that it clears the cistern lid, when it is full, and the float is at its highest position. DON’ T FORGET TO REPLACE THE FIBRE WASHER BETWEEN THE BRASS PIPE CONNECTOR AND THE NEW VALVE. AS IN TAP HINTS, CLEAN OUT THE GROOVE WITH A SHARP TOOL BEFORE FITING THE RED FIBRE TAP CONNECTOR WASHER. DO NOT OVERTIGHTEN THE CONNECTOR, REMEMBER THIS IS SCREWING ONTO A NYLON PART, NOT BRASS, AND THE THREAD CAN BE DAMAGED. IF YOU THINK THAT THE END OF THE NYLON PART (WHERE IT CONNECTS WITH THE BRASS 15mm TAP CONNECTOR) IS UNEVEN, AND HAS SOME PLASTIC “MOULDING FLASH”, SMOOTH IT LIGHTLY WITH A SANDING BLOCK AND FINE EMERY.


The less common problems are:

Failing to flush: This is usually due to a worn syphon. You can get a universal replacement for less than £4 (SCREWFIX NUMBER D19940). To repace this, you will need to isolate and disconnect the cold water feed, flush the loo to empty most of the water, and unscrew the two cistern screws anchoring it to the wall. Disconnect the overflow pipe, then unscrew the 2 wing-nuts holding the cistern to the pan. The cistern may need a tug, as the big “doughnut” seal can hold quite firm. Have a bucket ready to tip the remainder of the water into, take care not to splash on carpets, as it may contain bleach if you use those bleach blocks in the cistern. There is a LARGE plastic or alloy nut holding the siphon on to the cistern, and you will need a large spanner, or stilsons to remove it. The “doughnut” seal usually covers this. Never attempt to reuse it, you will nearly always get leaks, as the cistern rarely goes back in exactly the same position, and in any event, the new nut may seat differently on to the seal. Some plumbing shops will charge £3 or so just for the seal, but SCREWFIX do the whole close-coupling kit, with new clamp, washers, wing-nuts AND the doughnut shaped seal, for less than £2. The SCREWFIX number is D17405.
Leaking from the bottom of the cistern when flushed: either the cistern is loose on the pan (try tightening the wing-nuts), or the doughnut seal is worn or perished, or it was not replaced with a new one when the syphon was changed.


Particular attention should be paid to the diaphragm bleed pin when removing and re-fitting the diaphragm. It MUST be located so that the pin goes through the small hole prior to putting the retaining cover and ring back on, otherwise it will be damaged and become perforated and unusable. Also be careful not to loose the small seal between the lever and the cover if the lever is unclipped. Note the float rotates easily to adjust the water level.


Note the position of the fixed water-bleed pin, that equalises the pressure either side of the diaphragm, when the lever covers the small hole in the retainer/cover. This allows for a gradual and quiet shut-off. Note the flexible plastic tube that also reduces the fill-noise.

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