Unvented OSO SX - Mains supply

[tigboy]

Hi All

I will be getting an OSO unvented cylinder at some point and I'm trying to plan out my bathroom plumbing.

The installation manual ask for an uninterrupted 22mm main feed which i can run easily as i currently have no ceilings. It then informs me the balanced cold should only be used for mixer showers and bidets.

So my question is where do i get the other cold feeds for the toilet, bath etc?

For ease of use, I’d like to tee off the 22mm cylinder feed as it passes right by the bathroom. But i think the correct/best way is to tee just before the PRV on the top of the boiler.

Any help much appreciated!!

 

[CountryFan]

I haven’t heard that before with shower mixers and bidets. Have you spoken to your installer?

 

[tigboy]

No not yet, this is what the manual said in a CAUTION BOX -

Do not use the balanced cold connection to

feed any outlets other than mixer showers

and Bidets. Under no circumstances use the

balanced cold connection to feed all cold wa-

ter outlets as this practice contravenes Sec-

tion 10 of water regulations.

Unless its just means don't go down to your drinking tap?

 

[CountryFan]

It must mean that a tee off before it is balanced to be fed to all other outlets.

 

[Madrab]

Weird one that. Reg 10 of the water regs is about enforcement.

Not sure what section 10 they refer to would be then, unless it's something to do with backflow (part of the regs) or possibly stealing flow to the cylinder (not part of the regs). Do you have a link to the MI?

The whole point of the balanced feed from the combi valve would be to ensure all mixing outlets have the same pressured supplies to avoid flow issues, stand alone outlets could be run from the mains directly

 

[tigboy]

Yes - https://osohotwater.co.uk/wp-conten...1864-142228-12-OSO-SUPER-SX-VIP-MANUAL-UK.pdf

 

[tigboy]

For some extra detail, the Airing cupboard is the furthest point from the incoming main (stopcock) - The 22mm supply for the cylinder will pass under the bathroom and travel about 4m to the tank.

I was thinking it would be better to take the tee a close as possible to the cylinder, and then run back to the bathroom, giving the cylinder priority. Rather than having all my cold feeds drawn off before it reaches the cylinder.

 

[Madrab]

Nope - still doesn't make much sense - Section 10 is about enforcement - so not sure what they are talking about, unless it's a subsection of one of the other provisions. The only reason I can see, given the mention of air gaps is it's about backflow but that's under Parag 2 Sect 15. It would be interesting to call OSO tech and get them to explain what they mean by that, just for clarity.

All it means though to comply, would be to take the other cold outlets off the mains supply prior to the combi valve. Though in doing that it does mean that there could then be an imbalance at other mixed outlets, say a sink or basin. That kinda defeats the purpose of not using it, and means that ideally there would then be a mains PRV as well, set to the same pressure as the combi valve, to balanced the supplies at the other outlets.