(Tankless Toilets) Mains pressure flush toilets versus cistern flush toilets

Mains pressure flush toilets are appearing in more places - shopping centres, hospitality venues, etc. And it is possible to buy them for domestic residences too.
Obviously they need backflow prevention devices (BFDs).
My main question is: What water pressure do they need to operate properly?
Mains water pressure and internal house water pressure has been mentioned in the topic about garden hose fittings and the point made that different water utility areas may have different standards for what is considered “too high a pressure” and “too low a pressure”.
Does having a whole of house water filter impact on practicality of installing a mains pressure flush toilet?
Could an electric pump connected to a water tank (pump triggered by ‘turning tap on’) provide sufficient pressure?

And finally any other comments on mains pressure flush toilets from people with experience of them, please.

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Are there a number of different solutions?

This one from Toto appears to have an integral pump system with minimum water supply of 70kPa.

Others suggest 400kPa supply pressure.

I’ve a similar question to @vombatis wondering about the flow rate required from the mains or house pressure pump.

Not about to race out and buy one at Mr Harvey’s special price, even of it is a Toto product.


Seems like quite a few other retailers have the same price, $8599, for Toto Neorest AH CS985PVC + TCF9786WAT

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Another brand and option, but again from the premium end of the market. I wonder if there are $1000 versions of the system. The pedestals appear to be different internal design compared to a standard rimless.

And another take on no cistern, but uses a tank integrated with the pedestal.

My research so far suggests the commercial installations rely on consistent high water pressure which may explain why some of the cisternless residential systems include a pressure pump. There may be more useful content available looking for details of the products provided for commercial and mass public service installs?

For water efficiency they seem no better than my basic choice. Something to inspire :joy: and a brand that powers our zero turn mower (Vee twin of course).

Every MP should have one!

I think the rest of the world calls what is being discussed ‘tankless toilets’. Cistern is so old world Latin and harder to spell correctly.

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Possibly. It may also limit flow rate. I take it that the reason a certain pressure is required is to provide a minimum flow rate.

One can always reduce the pressure if that is needed. Often hot water systems have a pressure reduction valves on the inlet side to prevent the overflow valve releasing all the time in districts with high mains pressure.

Yes. Such pumps are standard for those on tank water. You can choose the pressure you want to suit your circumstances. Each model will provide data on maximum pressure and flow rates. Multi-stage pumps that are more capable are more expensive.

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The one elusive fact so far is the flow rate required at the operating pressure nominated for the tankLess toilet system. Our house pump can be set to operate at more than 500kPa but the flow rate drops to a dribble. The size of the delivery pipe to the toilet will also restrict the flow. The static pressure may say you have sufficient but the dynamic pressure at the toilet could drop to below that required for proper operation.