Bidet sprayer using toilet cistern and water heater

[Luke2790]

The OH has asked if we can fit a bidet sprayer in our standalone WC that we're currently renovating. Trying to do this within regs, (without spending a fortune), it seems, is virtually impossible. WRAS seem to suggest a DC pipe interrupter could be used, however as the sprayer would be isolated once it's turned off, this would likely cause the valve to leak... so that's no good and there goes my 'cheap' option.

My second option is to provide an AA air gap. My question is: as I am fitting a new (plastic) cistern and concealing this above the room for reasons I won't go into, would it be a terrible idea to take a separate feed out of the cistern to then provide flow for the bidet spray? This would effectively save me from fitting a second cistern... unless anyone can recommend anything different!

I could then feed this via a small water heater. I anticipate that the pressure should be enough from a gravity-fed supply to not require a pump as well.

Anyone got any experience with these?

Thanks

NB: I'm also aware that this is notifiable work but unless I can find a reasonably inexpensive way of making it work then it won't be happening anyway!

 

[Madrab]

When you say bidet sprayer, do you mean a ablution/douche type spray device? They don't work well on gravity type systems unless pumped TBH.

If following the regs, you cannot use the same cistern to supply other outlets that aren't classed at the level as the cat 5 appliance, unless the supply to that appliance has CAT5 backflow protection. What is this cistern you are installing above the room to be used for?

 

[Luke2790]

Thanks Madrab, yeah you got it.

I wasn’t aware of the regulation you mentioned but as the cistern is for the WC, as that is also cat5, am I correct that it would be ok to use that as my supply?

The pressure was a concern so I might give up on the idea unless I can find a small water heater/pump combo.

Thanks

 

[cdbe]

I have a vitra aquacare toilet with built in bidet, works well.

 

[Madrab]

When trying to interpret the regs in some cases it can become quite confusing. I think they make them deliberately 'open to interpretation' so they won't be used to beat the authorities up with and also allow a semblance of professionalism and best judgement/common sense to be applied, when it comes to implementation.

With these one specifically, on one hand, it states for a CAT5 appliance that CAT5 protection is required for backflow and back pressure, on the other they say that an AUK1 air gap is sufficient but that only provides CAT3 back pressure protection. Some say it is better to err on the side of caution and provide for the former.

Using a WC fed from a cistern provides an AUK1 setup where the toilet has the interposed cistern (as long as it's using the correct fill valve) that however does not provide CAT5/CAT5 for the ablution device. Therefore ideally the cistern would be of a type that provides either AA or AB protection and then use a micropump to boost the supply to the douche. That isn't the cheapest to implement. It all comes down to how stringent you want to be I guess. As long as CAT 5 backflow protection is implemented, then is CAT3 back pressure protection OK, is really the question.