Unusual flange required for WC cistern overflow/warning pipe

[Carl Haworth]

The WC is in a downstairs bathroom. on an outside-type house wall that has my workshop on the other side. There is a outdoors-type gully in the concrete floor of the workshop for the wastes from the bathroom. The end of the overflow pipe from the WC cistern is in same place, and is visible from inside the workshop, so dripping would go into the gully, and would be noticeable..

The water in the trap in the gully gets smelly, as the wastes which run into it are not used often enough. If I clean out the gully trap, the smell goes - but soon returns. This makes the bathroom smelly also - surprising as this may sound! I proved this by temporarily disconnecting the cistern overflow pipe from the section which runs through the wall. I fitted a length of pipe to the existing elbow off the cistern flange and ran this down into a container. I plugged the exposed end of the original pipe where it runs through the wall.

No smell now. The ballvalve is in good order, so no water has accumulated in the container. But the solution creates a flood risk: the ballvalve might fail, and do so seriously enough to direct water into the container at the full mains flow rate.

(BTW, for reasons beyond the scope of this enquiry it is not feasible to solve the problem by changing the low level WC cistern and pan to the modern type which overflows into the pan.)

So I need to revert to the original arrangement, but blocking the smell at the same time!

I can do this by extending the overflow pipe inside the cistern, directing this extension down to reach well below the normal "full" water level. The overflow would still work up to the maximum flow rate that overflow pipe allows. Its "warning pipe" end in the workshop would still be visible.

To make this change I need a flange(?) for the warning pipe hole in the cistern which allows:-

1. The existing connection (short pipe leading to elbow and thence through the wall, blah, blah) on the outside of the cistern, and

2. A similar connection on the inside, or some sort of hopefully neat bodge enabling me to fix a short piece of pipe to the cistern side of the flange. I could then fix a short length of pipe to the flange, plus an elbow, or an elbow straight off the inside end of the flange, and then a down-run of pipe, so as make the entry to the overflow pipe well below normal "full" water level.

So I seem to need some sort of 21 mm overflow-pipe double-ended flange, or a "neat bodge" means of achieving the same result.

Any ideas would be much appreciated!

 

[Madrab]

Change the flush valve for one that overflows into the pan, plug the hole in the cistern and remove the overflow pipe run

 

[just pumps]

Change the flush valve for one that overflows into the pan, plug the hole in the cistern and remove the overflow pipe run

Yep keep the pan n cistern you have and change the flush valve.

 

[Carl Haworth]

Thanks to you both, but I did mention that our downstairs WC consists of a low-level cistern and (separate) pan, and that it is not feasible to change this.

I'm still looking for a way of connecting overflow pipe to the inside section of the flange fitted to the cistern.

In the modern close-coupled combo there is a flush water port in each component. These line up, and are sealed to form a short, concealed, duct. Overflow is direct into the pan through this duct. There is no external flush pipework in between, as is the case with the low-level combo where the flush water passes from the cistern into the pan via a curved piece of tube called the "flush pipe" (or "flush bend").

For overflow direct into pan to work, the two units have to be a matching close-coupled pair. The flush is via a dump valve rather than via a syphon. The lower head (water pressure) of a close coupled cistern means that the flush water duct from the cistern into the pan has to be of much larger diameter than that of a flush pipe. This large diameter obviously allows the cistern overflow to be within the flush duct.

This modern type of flush can be wasteful of water because many people do not realize that water trickling down into the pan when the WC is not in use is a warning that the ballvalve is either not closing fully, or is, but is leaking, and needs attention. Or they do realize, but don't do anything because the discharged water is not creating a nuisance. For such reasons, for many years when this type of WC was common on the continent of Europe, it was not allowed by water regulations here,. I don't know how, if at all, the design was modified to allow it to meet our regulations, or if this veto was simply withdrawn while we were members of the EU - to allow us to comply with the regs of the European Single Market.

 

[Madrab]

Thanks to you both, but I did mention that our downstairs WC consists of a low-level cistern and (separate) pan, and that it is not feasible to change this.

For overflow direct into pan to work, the two units have to be a matching close-coupled pair. .............

not sure who said all of that stuff BTW, because that just isn't right, it's not just close coupled toilets that can use internal overflows.

A low level cistern can use any flush valve - syphon or otherwise, with exactly the same 11/2" or 2" outlet , it will fit a low level cistern and flush pipe quite happily and a lot have internal overflows.

Honestly, have replaced/converted many of them and it solves all the problems in one go.

This is the fluidmaster one - Opella do another and it could even be coverted it to a drop valve type too with a euro flush pipe kit to name one.

Fluidmaster Dual Flush Syphon

DualFlush Siphon 8" with internal overflow.• 8” Dual Flush Syphon for 1 1/2” Outlet Toilets• Easy to Install• Capable of 4/6/7/9 litre flush• Internal Overflow• Water-saving Dual Flush• Partial Flush achieved by depressing the lever and holding down• WRAS approved• Supplied with 2 ½” C Link

www.toolstation.com

 

[Carl Haworth]

Yes of course you're right that a syphon overflow can be used- in principle!

Not in practice, though, in this case! A syphon will overflow into the pan if the water level rises above the bottom of the highest point of the syphon tube. But our cistern is a Dudley "Elite".
So I'm still looking for a way of connecting overflow pipe to the inside section of the flange fitted to the cistern.

FYI this cistern needs a 9.50" syphon, for two reasons;-

1. This cistern is slim from front to back, so wide and tall. This is because the room is small, so I needed the minimum possible pan projection from the wall, which, to ensure that the seat stayed up when raised(!), meant a very slim cistern. To give a full flush of 9 litres, which the pan needs for "serious work" the syphon had to be uncommonly tall.

2. It also has to be tall because there is a shortish internally-threaded spigot moulded into the top of the syphon tube. This extends to just under the inside of the top of the lid, and allows this, which, like the cistern itself, is quite lightweight, to be clamped down by a recessed screw passing through it. This makes the assembly rigid enough to stand the forces applied to the front panel when operating the flush (well, it hasn't cracked - FLW?).

The height of the "floor" of the inside of top of the syphon tube means that water reaches the handle hole before the bottom of the overflow outlet. This could be overcome by using a shorter syphon with a longer screw, but the cistern would not then flush satisfactorily, at least on half-flush.

I do know that, because, when this bathroom was created by turning a very small and useless "lobby", interconnecting with a reasonably sized shower/WC room, into a bathroom, the increased popularity was accompanied by a drainy smell (possibly the result of use that had now increased, but was insufficient to keep the water in that gully sweet-smelling!) It took me some time to identify the source of the pong. When I did, I wanted to modify the overflow to isolate it from the gully water. I knew that overflow via the syphon might be a simple solution, but I found, with the 9 .5" syphon, that water emerged via the handle hole before it had reached the overflow outlet. I then did try a shorter syphon. Result: overflow OK, but flush not of sufficient volume/velocity. Ay, ay, ay!

I still post in hope!