Stubborn ancient bib tap

[JohnW2]

A tap incorporating a check valve is ok in your situation, you are replacing an existing tap.

As I said, although I may be wrong, I would have though that, in my situation, it would be OK even if it were not replacing an existing tap - since the tap would still be supplied via a check valve that was 'inside the house', even though it was also 'inside the tap'.

If it's true that the existing 'isolator' is theoretically non-compliant because it isolates something else in addition to the tap, than that is so daft that I would happily ignore it

In passing, I would say that all this excitement about check valves in this situation seems to be addressing an incredibly improbable 'problem', since backflow into the supply network would require the pressure in the network to fall to near-zero at the very same time that the end of the hose was submerged in some 'contaminated' water (itself a very unusual situation). Am I missing something?

Kind Regards, John

 

[denso13]

Am I missing something?

Not really. Unusual yes, impossible, no. All helped by a cheap check valve.

 

[denso13]

As I said, although I may be wrong, I would have though that, in my situation, it would be OK even if it were not replacing an existing tap

Yes, the servicing and check valves regs apply to taps "outside".

 

[JohnW2]

Not really. Unusual yes, impossible, no. All helped by a cheap check valve.

I would say that's somewhat of an understatement - as I said, I would have thought it was 'incredibly improbable'. It's like many of those things we discuss in the Electrics forum - very little is totally impossible, but some people get excited about 'issues' which can only arise if two things, both of which are extremely improbable ('very rare'), happen simultaneously.

Kind Regards, John

 

[JohnW2]

Yes, the servicing and check valves regs apply to taps "outside".

True, although I would say that a tap with a hose connector located very close to a door to the garden comes within the 'spirit' of an 'outside tap'.

... a bit like the earliest requirement for RCD protection of electrical sockets - which only required such protection for sockets "likely to be uswed to power outdoor equipment'.

However, as I've said, even if one regards the '(inside') tap as being effectively 'outside', I still think that the check valve requirement would (should!) be satisfied by what I am proposing -0 since the check valve would not only be present but would also be 'inside'!

Kind Regards, John

 

[denso13]

I would say that's somewhat of an understatement - as I said, I would have thought it was 'incredibly improbable'.

I don't think it is as rare as you think.

I still think that the check valve requirement would (should!) be satisfied by what I am proposing -0 since the check valve would not only be present but would also be 'inside'!

Well, yes, I've said so a few times now.

 

[CBW]

but some people get excited about 'issues' which can only arise if two things, both of which are extremely improbable ('very rare'),

I don’t get excited about water regulations, but I try to advise and adhere to them as best I can. I attended a job last week where the filling loop was left connected on a heating system, and the check valve had failed and the hating side of the loop was left open - the result = Brown/black water entered the drinking water supply, so not as rare as you think.

 

[Harry Bloomfield]

As I said, there is a practical/access issue with a pipe longer than about 18" - there is a wall very close on one side of the tap and the basin (with it's pipework and waste) very close on the other side. However, I'll see if anything longer will fit, but am putting my greatest hope in heat.

One 'spanner' on the tap, something else helping to take the torque on the pipe, so the arms of both are at a similar angle, close to each other - then fit a lever between them, to apply the brute force.

 

[JohnW2]

I don't think it is as rare as you think.

Maybe you're right, but I find it very hard to understand/believe.

It obviously depends to some extent on what one does with the hose. Speaking personally, I would say that I have virtually never used a hose with its 'end' surrounded by anything other than air! Furthermore, if the supply pressure were so low that backflow was a possibility, one would presumably abandon attempts to use the hose.

About the only situations in which supply pressure reduces to 'near zero' (or negative) are when there is a breakage in an underground supply pipe - and in that situation, water in the distribution network will have been 'contaminated', anyway.

Kind Regards, John

 

[JohnW2]

I don’t get excited about water regulations, but I try to advise and adhere to them as best I can.

I, and many others, take the same approach in relation to electricity regulations, although there are some which seem to be so silly that it is hard to justify having to advise people to comply with them!

I attended a job last week where the filling loop was left connected on a heating system, and the check valve had failed and the hating side of the loop was left open - the result = Brown/black water entered the drinking water supply, so not as rare as you think.

That's surely a very different situation from what we are discussing here? Maybe I'm wrong, but it seems to me that even if contaminated water somehow gets into the end of a hose pipe (which itself must be pretty rare) it would require an incredibly iumprobable combination of ('rare') circumstances for that water to be able to 'backflow' through the entire length of the hose into 'other water' within the installation, let alone into the supply network. Do you disagree?

Kind Regards, John

 

[denso13]

About the only situations in which supply pressure reduces to 'near zero' (or negative) are when there is a breakage in an underground supply pipe

I know in big areas of Glasgow that the the fire service using water hydrants has a big impact on water pressures locally, some becoming negative which affects a lot of properties.

A check valve is a cheap solution, even if the possible back flow outcomes are not common.

 

[denso13]

through the entire length of the hose

Hoses come in various lengths. I think it's easier just to call a hose a hose.

 

[CBW]

That's surely a very different situation from what we are discussing here?

It is, but the point I was trying to make was, the check valve can fail, and therefore, if left say in a pond, the pond water can be back flowed into the supply.

let alone into the supply network. Do you disagree?

Yes, only because of how it was explained to me. A fire could break out and this can place a negative pressure on a main supply, and contaminated water could potentially get sucked into the supply. The same can be said for shared supplies, where one pressure can be greater than the next. They wouldn’t write it as a regulation, no matter how daft it seems, if it hasn’t happened or could happen.

 

[JohnW2]

I know in big areas of Glasgow that the the fire service using water hydrants has a big impact on water pressures locally, some becoming negative which affects a lot of properties.

I hadn't thought of that scenario, but I don't think it materially alters the generality of the probabilistic observations I've made - i.e. I would think it extremely unlikely that someone would have a hose pipe dipping into contaminated water at the very same time as the fire service were drawing water from a hydrant in the locality.

In any event, as I said, if supply pressure had become very low, or negative, it's unlikley that anyone would persist in trying to use a hose

A check valve is a cheap solution, even if the possible back flow outcomes are not common.

As with our electrical discussions, I will never knock people who want to be ultra-cautious in taking measures to address extremely small theoretical risks. However, as we're being told, check valves are not only a 'cheap solution', but a solution that sometimes fails - which somewhat complicates the discussion

Kind Regards, John

 

[denso13]

who want to be ultra-cautious in taking measures to address extremely small theoretical risks.

I know that's your view, it really isn't mine. Do you know how often backflow incidents happen?