External Hot

[i_am_fubar]

I'm in the process of plumbing in the new kitchen sink along with washing machine points (hot and cold) and a feed for the exterior tap (via isolator, NRV and with a drain point).

In the future, I would like to have an external sink with hot and cold water and want to make allowances in the plumbing now. I imagine I will still need the drain points and isolators for when the weather turns cold, but is the NRV still needed as it is only a mixer tap, rather than a hose pipe that is being fed. Or is an NRV needed for all external plumbing?

Cheers,
Fubar.

 

[Charnwood]

Is/will the mixer spout single or dual flow?
Single flow; DCV.
Dual flow; no DCV

That's regardless of indoors, outdoors.

 

[i_am_fubar]

How do you mean duel flow? Is that such that if the water is mixed in the tap it is single flow (and risks pumping water back into the other side if there is a pressue imbalance). If the water comes out of two orrifices next to each other such as to simulate mixing, it is duel flow and that issue is negated?

Does the fact I have a combi boiler change that?

If that is the case, I need to add valves to some other taps

What if it is two single taps? does it then count as a hose point?

Cheers,
Fubar.

 

[Charnwood]

I do not mean duel flow, that's muskets at dawn. I mean duAl flow.

Your assumption re the spout is correct.

Having a combi does NOT alter it. Why do you think you are told not to drink the mains fed hot water from a combi? Not because it's hot. It's no longer classed as potable and the water authority don't want it back, thank you very much.

How can two taps be 'A hose point'? Surely they are two hose points.

 

[i_am_fubar]

Wow... I've never been stung by a grammar Nazi (colloquial, non offensive use there) before... I totally blame my work computer not having the spell check add on... But still, ouch

However, thanks for the info all the same. I had thought that the reason hot was generally deemed not potable, was because of the dead rat in storage tank issue, but I guess a heater, pump and additional plumbing will add contaminants.

The reason I asked if it was different with a combi was because the pressure would be more equal than a mains pressure cold vs. gravity fed system. Though I can see there would still be a risk.

While I know it's daft from a flow rate front, but if the out door tap was fed from a loft tank, surely that would negate the valve issue as there is no chance for back contamination?

And, yes, A 'couple' of hose points then (can I get away with blaming that on a typo? ). I was only thinking about the cold though. Does the hot still need one as contaminating already non potable water isn't an issue?

Cheers,
Fubar.

 

[Charnwood]

Duel is a word, so a spell-checker would not indicate your error.

Back-contamination/back-syphonage refers to water being syphoned back into the mains cold water system, be it tank water, combi hot water, pond water or otherwise.

Fixed-height tap spouts should be above the spill-over height of bath/basin/sink to prevent syphonage. If, for whatever reason, they are not then DCVs are the order of the day if either/both are fed from the mains.

Gute nacht.

 

[i_am_fubar]

Touché my good man.

Took a while to wrap my head around what you said and form it into a nice mental diagram, But I now understand syphon issues that are associated with both hose pipes (or other peripheral water systems), and poorly installed taps.

So those tap clamp on hose adaptors are generally a bad idea? Or do they have NRV's built in?

Annnnnnd, If a tap is just a tap (as in a bathroom style), and the spout is above the rim of a sink, then whether inside or outside, it has no syphon risk, and as such, doesn't need NRV?

I've got no problem fitting them if I need to, I just want to make sure before I start plumbing it all in and wasting those precious pennies.

Cheers,
Fubar.

 

[Charnwood]

So those tap clamp on hose adaptors are generally a bad idea? Or do they have NRV's built in?

Wouldn't touch one with a barge pole. And no, no DCV.

If a tap is just a tap (as in a bathroom style), and the spout is above the rim of a sink, then whether inside or outside, it has no syphon risk, and as such, doesn't need NRV?

Individual taps, no. Mixers, again, it's down to the spout.

Just a point on TLAs - NRV stands for Non-Return Valve. This can mean single or double check valve. When dealing with back-syphonage to the mains it has to be a double, hence me using the TLA DCV.


((TLA: Three Letter Abbreviation/acronym.)

 

[i_am_fubar]

So, all DCVs are NRVs. But not all NRVs are DCVs

As it is I've already got DCV's for the hose point. So assuming I use a dual flow tap outside, or two singles, I don't need to worry about installing another. Just some way to drain it down in winter.

Cheers.

All I have to say to your note on TLAs is TSA

Fubar.

 

[Charnwood]

TSA? Is that the French one about learning disorders?

 

[i_am_fubar]

Teaching to Suck Eggs (for what TLA stands for at least).

Didn't get spare DCVs for the tap, but figured I would get the rest of the plumbing done. And dang, I experienced the effect of not having them first hand... Why is there water pouring out of the hot pipe when only the cold is on?!

Maybe not pouring out, but I had a bit of a leak. Lesson learned, don't re-use old tap hoses.

Fubar.