What are the pros and cons of putting a downstairs toilet's cistern in an upstairs cupboard or converted loft, to save space in a tight cloakroom?

Question

As the question says. I have a tight downstairs cloakroom in my house, that I'm redesigning. The inches taken up by a typical cistern behind the toilet is a problem,it pushes the seat too close to the wall for easy use. An old fashioned "up on the wall with a chain flush" is a non starter aesthetically (to me, anyway!). But many toilets in shops and offices have touch or heat sensitive (contactless) flushes, and this gave me an idea.

Suppose I put the cistern in another room above, either in a cupboard or void space on the upstairs floor (1st floor UK, 2nd floor USA), or in the converted-bedroom loft. Then in the downstairs cloakroom I provide a pressure sensitive or touch sensitive flush button on the wall instead - but no cistern in the cloakroom, just the slim downpipe.

One problem I can imagine is water pressure might not be enough for siting in the loft, but that won't be an issue for the upstairs floor if so. A second issue might be sporadic noise at all hours - but I imagine most of the noise is in the water rushing into the toilet, not in the cistern or its refill, and I would hope to resolve this with muffling, boxing in, soundproofing etc, so the cistern end upstairs is near-silent. A possible advantage could be greater inrush to the toilet and perhaps a more effective flush?

Has anyone got experience of such a setup?

What would the pros and cons (if any) be? How big a problem would noise be upstairs, or muffling it? Are there any substantial reasons I should reconsider not doing it this way?

Answer 1

Have you considered a toilet with it's cistern/tank built into the wall behind the toilet - like this set?

tank (amazon)

toilet (amazon)
_{Just examples, not recommendations}

As long as you have or can make space between the studs in the wall then the tank takes up no space at all.

I installed one of these about a year ago, and I find that it flushes better & more reliably than any other toilet in the house.

Answer 2

The typical commercial toilets that don't have a visible tank don't have a tank at all. Instead they use what is commonly referred to as a Sloan valve. There are likely some other brands, but Sloan has been around a long time and is definitely what I see (if I bother to look closely enough at the fixture) in commercial bathrooms.

A quick search seems to indicate you can install this type of toilet in a residence, though there may be issues depending on your water pressure, and I suspect the fixtures are not inexpensive, because they are designed for heavy duty use - hundreds of flushes a day.

Using a tank but moving it to a different floor is looking for trouble. Additional pipes. Additional places to leak.

Answer 3

You mentioned the possibility of greater inrush. At rest, when the cistern is filled and ready for use, the level of the water in the cistern might be some 30 cm above the rim of the toilet bowl. Because of the weight of the water itself that difference in height gives rise to a static pressure of 3 kPa (measurable at the flush valve at the bottom of the cistern).

If the cistern were elevated to the upstairs floor, perhaps 2.4m higher than its normal position, it'll develop about 24 kPa static pressure - substantially higher than what's normally expected.

Whether that's a problem is anybody's guess, and it'll probably depend heavily on the hydraulic design of the toilet in question. Bowl cleaning, flush performance, or splashing could be affected for better or worse. If the additional height/pressure causes the cistern to evacuate more quickly than normal it may increase the risk of bowl overflow. Usually a bowl and cistern are sized so that an entire flush can be contained in the bowl, but if this re-arrangement of the cistern resulted in the valve being at toilet level and the volume of the downpipe being added to the volume of the cistern, it could be problematic.