I recently heard my cistern overflowing. On investigation I decided to adjust the float level to stop it by reducing the height to which the water in the cistern rose when it filled. A few days later I heard the distinct sound of the cistern overflowing again. I then realised I needed to repair my Toilet Silent Fill Valve.
In order to satisfy the requirements of Internet SEO (Search Engine Optimisation) the valve is referred to, in this article, specifically as a Toilet Silent Fill Valve or more generally Silent Fill Valve but its full title is a Silent Fill Toilet Cistern Inlet Valve since it is:
- An Inlet Valve.
- A Cistern Inlet Valve.
- A Toilet Cistern Inlet Valve.
- A Silent Fill Toilet Cistern Inlet Valve.
Repairing a Silent Fill Valve used in a toilet is, in my opinion, easier to perform than one on a traditional ball valve (ball cock). Modern inlet valves take up the minimum of space with their small float, are made of plastic and can often be dismantled by strong hands without any spanners because their screw threads don’t jam with calcium and corrosion like brass ones. They are available in various formats. Some mount through a hole in the side of the cistern, and are a good replacement for old brass ones (which are usually mounted that way), while others stand on a tubular stalk inside the cistern which mounts through a hole in the bottom of the cistern. When the fill pipe is attached at the bottom of the cistern the pipe can often be situated out of sight. Bathrooms look much nicer and cleaner when pipes are out of view.
It may be that a Replacement Fill Valve is required. If so take a look at my article “Replacing A Toilet Fill Valve”.
To find out how a Toilet Silent Fill Valve works see the addendum to this post entitled:
Why Is It Silent?
This type of inlet valve is referred to as silent because it is designed to fill the cistern quickly (mine takes about 30 seconds for a small flush and 45 seconds for a large flush) and without the sounds of rushing and splashing water within the cistern. The silence is mainly achieved by keeping the outlet of the inlet valve below the water level in the cistern.
If the inlet valve outlet fed into the water through a solid round pipe it would be susceptible to becoming a syphon under adverse conditions when the supply pressure is low, e.g. when the water supply to the house is turned off. Water could then syphon back into the supply pipes1. The water authorities are very keen to prevent that, with any connected apparatus, in case the water main gets contaminated by it. People in the same building could end up drinking the water siphoned back.
In the past they would not have allowed any inlet valve outlet pipe to be immersed, but by using a collapsible polyethylene pipe for the outlet (its like a narrow polyethylene bag with a hole in the bottom) siphoning can’t take place. The flexible polyethylene pipe doesn’t float up and lay on the water surface because it has a thin plastic rod inside it which keeps it pointing straight down. I think that if it did float on the surface water might spray in all directions within the cistern. Remember they don’t have watertight lids since air has to get in to replace the water when it is flushed out.
When the cistern is filling I can still hear water flowing in the house pipes, but only for a short period.
My Ideal Standard Toilet Silent Fill Valve was supplied with my Armitage Shanks toilet in 2007 and has served me well needing very little float level adjustment and no replacement parts in the intervening period up to April 2014.
Gaining Access To My Silent Fill Valve
To perform any operation inside the toilet cistern the lid must be removed. I have already posted an article describing how to do that on a modern push button toilet like my Armitage Shanks Ascania WC. You can read it here entitled ‘Dual Flush Toilet Cistern Lid Removal’. With older ceramic cisterns that are close coupled to the pan, or just above it, the lid usually just lifts off. I’m sure some plastic cisterns have some screws around the edge of the lid holding it on.
My Internal Overflow
My cistern overflows internally through a pipe rising from the bottom of the cistern. (See adjacent image.) The output from this overflow pipe drains straight into the toilet pan at the point where the flushing water enters.
Why it took a century to develop an internal overflow I don’t know. All the problems with external overflows disappear with an internal overflow.
The problems with external overflows are:
- Water pouring all over the paths outside and then freezing in winter in cold climates.
- Water pouring down the wall of a house where the overflow pipe is too short or doesn’t hang down or the wind blows the water back to the wall. Unattended this can seriously damage a wall causing damp, mortar erosion, mould and bad staining which then ruins the look of a property.
- Icicles hanging from overflow pipes which break off and injure people underneath in cold climates.
- Water in the overflow pipe freezing whilst overflowing in cold climates causing the overflowing water to back up and spill indoors.
- Toilets need to be near an outside wall or have a lengthy overflow pipe on the inside of the building.
- Cold air blowing into a clear overflow pipe from outside and passing across the top of the water in the cistern. This can chill the water in the cistern by evaporation until it freezes. (The overflow pipe should turn down into the cistern water so that air cannot pass through the pipe.)
My Silent Fill Valve Parts
Once the cistern lid has been removed the Silent Fill Valve is accessible on the left of my cistern. Here you can see the parts labelled:
When I first detected that I had water overflowing from my cistern I removed my cistern lid and adjusted the float of my Silent Fill Valve, by turning the long screw attaching it to the arm, so that the cistern water level didn’t rise so high. The long screw has a hexagonal nut moulded onto it but it shouldn’t require a spanner to turn it, fingers are sufficient. See the image below where the Toilet Silent Fill Valve Top Cover and Arm have been removed to give a better view of the Float Adjusting Screw:
Adjusting my cistern’s water level:
To raise the water level: I turn the screw clockwise , i.e. screw it into the float.
- To lower the water level: I turn the screw anticlockwise , i.e. screw it out of the float.
NOTE: There is a line marked in the porcelain showing where the water level should be when the cistern is full.
Flushing The Cistern With The Lid Off
The cistern can be flushed with the lid removed by poking something suitable through the holes in the Height Adjustable Securing Plate and using it to push the flushing buttons down. Either a button with spindle attached or a screwdriver can be used. Where space permits the buttons can be pressed directly with a finger or thumb. For more information refer to: ‘Dual Flush Toilet Cistern Lid Removal’.
Turning Off My Cistern Water Supply
When adjusting the float failed to stop my cistern overflowing I presumed there must be a problem with the Toilet Silent Fill valve itself, probably the rubber diaphragm within the Toilet Silent Fill Valve. I decided to examine the rubber diaphragm by taking it out of the plastic body. That required me to turn off the cold water supply to the cistern. I have an inline stop tap installed as part of the flexible hose linking the copper supply pipe, where it exits the wall, to the Toilet Silent Fill Valve Support Tube protruding from the bottom of the cistern. So I just had to rotate the tap with a flat blade screwdriver until the slot was across the pipe instead of inline with it.
NOTE: This type of tap usually turns both ways and through 360°. See images below:
Repairing My Silent Fill Valve
To repair my Toilet Silent Fill Valve:
I began by unscrewing the Clamping Nut in an anticlockwise direction. This holds down the Top Cover of the Toilet Silent Fill Valve and seals it against the outer edge of the Rubber Diaphragm.
NOTE: There is a detent protruding from the top of the output pipe which engages the Clamping Nut. I had to force it out of the way of the ridges on the nut so that the nut could be turned.
Then I removed the Top Cover to reveal the Rubber Diaphragm inside:
NOTE: The Top Cover retaining the Clamping Nut can be removed without disconnecting the linkage from the Silent Fill Valve operating lever to the float. The whole assembly can then be moved aside by pivoting it on the float adjusting screw (not shown in this view).
The Rubber Diaphragm then has to be winkled out revealing the innards below:
At first I couldn’t see much wrong with the diaphragm but on closer inspection, when I stretched it, I found several splits in the rubber.
Here the diaphragm is pinned, in the stretched position, to a block of wood covered in white paper to display it:
Why do the rubber diaphragms tear? — T K Mukasa
Every time the diaphragm goes up and down the area that tears is bent, straightened and stretched. Eventually the molecules rip apart at a place in the material where they are overworked.
The real question is how many times should you be able to bend, straighten and stretch this material before the damage is done? I suspect if it were to be used on a device taking a long space journey it would be able to do it millions of times but it would cost a small fortune. What have we here? A twopenny-halfpenny device, so it only lasts a few years. Perhaps a better design or a better material that isn’t prohibitively expensive might make it last longer.
. . . I found your site, looked at the diaphragm and quickly spotted the tear. 10 minutes later and £1.57 later problem solved. — Richard King
Replacing The Diaphragm
. . . I then found an own Plumbsure brand replacement at B&Q which works perfectly. Part No. WB540QV3 diaphragm washer for quiet fill valve. — Mike Robinson
“This part can also be obtained from Screwfix where they are known as a “Hushflow Washer“ — HC
I couldn’t get a replacement diaphragm from Wickes but I did get one from B&Q, and here it is held in its operating attitude with the little red Restricting Pin pulled down by gravity. It doesn’t drop out of the hole because the other end of the pin is squashed flat making it too wide to pass through the hole. Make sure the pin can move up and down with ease under gravity while submerged:
The diaphragm is flexible so that the section which shuts off the main flow of water, when filling the cistern, can go up and down relative to the area which seals against the inside of the Silent Fill Valve Tube.
Cleaning The Parts
Before I reassembled the Silent Fill Valve I cleaned various parts. It’s quite easy to disconnect the adjustable float screw from the valve operating lever. The lever has a slotted hole and the plastic is flexible so it can be stretched to go over the ball on top of the Float Adjustment Screw. Only after disconnecting the lever from the float can the inside of the valve top be inspected. Below is the Top Cover Assembly:
Calcium can be removed from all the parts with the help of a descaling agent from somewhere like Betterware and the aid of an old toothbrush and a penknife to scrape with. It’s important not to damage the plastic around the pinhole in the Top Cover or the valve won’t function correctly (it may leak). See image below with Clamping Nut detached:
With care I prised the supports on the Top Cover sideways to release the fulcrum pivots of the arm so it could be removed. I was concerned that the supports might break under force. The supports are shaped so that the arm pivots can be clicked into place easily. (I suspect the manufacturer only expected it to be assembled once.) Below is the valve with the arm removed: You can see the underside of the arm with the Rubber Stopper insert to seal the pinhole in the Top Cover below:
NOTE: The rubber Stopper may need replacing if the dimple in it becomes too deep. The dimple’s made when it presses down, over a long time, on the proud Pinhole Cone on the Top Cover. I presumed, incorrectly, that the Stopper was a simple rubber cylinder and expected it could be removed and turned end over end to present a new flat surface with no dimple. However I have been informed by a reader, Tom Fenwick-Brown, that the Stopper rests on a spindle and so has a hole in the opposite end thus preventing that type of repair. I have not had occasion to remove my Stopper and look at the hidden end.
“Just one tiny (but important) point regarding your suggestion to: – remove the ‘stopper’ in the arm and turn over to present a new flat surface. This is not possible as the stopper is hollow and sits on a spindle, so the bottom side is open. I was unable to find a replacement anywhere, so I improvised with a shim under the stopper to raise the level and sort the problem. I tried a few tiny rubber washers first but found them too thick. I ended up using a cut out from an old pair of thin rubber gloves, which worked a treat. — Tom Fenwick-Brown
Reassembling The Silent Fill Valve
As is often the case reassembly of the parts was the reverse of the dismantling process.
I began by clicking the Arm into the forks of the Top Cover and threading the Clamping Nut over the Arm until it fitted around the Top Cover.
Then I seated the new Diaphragm in the top of the Inlet Valve body and fitted the Top Cover over it.
NOTE: There is a spigot on the edge of the Top Cover which can be positioned into one of three recesses on the valve body. The spigot will prevent the Top Cover rotating while the Clamping Nut is tightened. The spigot should be engaged with a recess according to the position of the float.
I Held down the Top Cover by screwing down the Clamping Nut in a clockwise direction.
Then I pushed the ball on the end of the Float Adjusting Screw into the slot at the end of the Arm.
All I had to do then was turn on the water supply and adjust the Float.
Flow Restrictors & Filters
A Toilet Silent Fill Valve may have a flow restrictor and/or dirt filter to prevent cisterns filling at too great a rate, in high water pressure areas, and filter grit out of the water which might interfere with the valve. A restrictor effectively narrows the fill pipe by adding resistance to the flow of water. Allowing the cistern to fill too quickly can adversely affect other appliances attached to the water supply by taking all the water and dropping the pressure at other points on the main. Showers are one appliance that require pressure to be maintained for them to work correctly.
Restrictors are not usually required if a cistern is fed from a header tank which is only one or two floors above since the pressure from such a tank will be low.
Many a Toilet Silent Fill Valve is supplied with the appropriate restrictor and the plumber decides whether to insert it or not. Some have a low pressure insert to put in its place if the restrictor is not required. What and where it is inserted depends on the design of the Toilet Silent Fill Valve.
Below there is a quote taken from a comment to this post by someone who resolved a filter problem with a Toilet Silent Fill Valve slightly different to mine.
“. . . I then remembered, before replacing the diaphragm, that underneath it – in my float arm cap – there’s a filter unit. Shaped like a small bullet – I’d pulled this out to flush it through as the instructions for the float arm, which I have, said to do periodically.
Anyway, I finally realised I’d not pushed this filter unit back properly into the recess under the diaphragm. Thus the diaphragm couldn’t even begin to do its job as it wasn’t being pushed down onto the valve as the cistern filled up! I pushed it firmly in and voila – the waterfall stopped!
So just in case others also have this little filter unit underneath their diaphragm – ensure you push it firmly back into the recess before replacing the diaphragm. Use a pair of long nosed pliers to twist the filter one quarter turn clockwise once it’s firmly pushed in place. The filter has little lugs on it which you can grip with the pliers.” — Marianne Wilford
My Silent Fill Valve Has Been Superseded
My Toilet Silent Fill Valve seems to have been superseded by a similar Toilet Silent Fill Valve with 18 ridges in the diaphragm which rest on 18 supports. See below:
As far as I can see the top is removed by an anticlockwise quarter turn twist to gain access to the diaphragm. Take a good look at the MTS video below showing the diaphragm being replaced:
I have noted that the plumber is not replacing the diaphragm with one with 18 ridges. I think it is also not an Ideal Standard type since it doesn’t have a blue float.
If an Ideal Standard diaphragm with 18 ridges is required then here is a source – My Toilet Spares (MTS).
1. How A Silent Fill Valve Works
Go to my reference article in the Reference Library entitled ‘How A Toilet Silent Fill Valve Works’ to see the detail in an addendum to this post.
2. Encyclopedia of Toilets
- How water could syphon back into the supply pipes and be a danger: If the stop cock is turned off in the street or the stop tap is turned off in the house then if the cold tap downstairs in a house is turned on water will come out of that tap from above if an upstairs tap is turned on (letting air in) or if water from an upstairs cistern can syphon backwards out through a valve which is not held shut. That cistern water is not guaranteed to be clean and could have been in the cistern for a long time if the toilet was not regularly used. Once that dirty water is in the cold water pipework it could be drunk by someone.