External Air Admittance Valve ?

[JohnW2]

A fly screen? .... "1.4 AX110: The AX110 incorporates the same features as the AF110, with the exception of the inclusion of an insect/debris grill manufactured from Polypropylene...."

Yes, possibly - I mentioned that before (as the only apparent difference they mentioned). However, I found the statement ambiguous (which is why I wrote of "presence/absence" of the screen/grill) - since it is far from clear (at least to me!) whether 'the exception' means that it is the AX110, or all of the others (but not the AX110), that has such grille!

FloPlast strongly advise that confirmation of acceptance of the use of the AX110 is gained from Building Control prior to installation."

As I intimated I would probably do, I have now asked the question of the relevant LABC (slipping in a mention of "unsightly SVP installations"!), and await their reply!

Kind Regards, John

 

[JohnW2]

I recently wrote:

As I intimated I would probably do, I have now asked the question of the relevant LABC (slipping in a mention of "unsightly SVP installations"!), and await their reply!

I got a surprisingly rapid response to my query to the relevant LABC. The first part of hi response was:

The use of external air admittance valves on soil vent pipes is allowed provided it has the correct certification. It should be ensured that the drain run has a second open vent along its run / length so an adjacent property or second vent on the same property is available to vent the drain run still

... that is essentially 'as expected', although, as I have said before, even if an adjacent property has an open vent at present, one cannot really be absolutely certain that such will always remain the case. However, he then goes on to add a comment which totally undermines his initial statement, when he writes:

I would advise that the valve is situated 900mm above or 3m away from an opening window as in certain conditions the valve flap can remain in the open position

That would obviously completely destroy the whole point of wanting to use an external AAV, since that whole point is to remove the need for the pipe to extend to "900mm above or 3m away from an opening window". I'm not sure whether he "just doesn't understand" or is just trying to 'protect himself' - but, whatever, the combination of his two statements seems to be plain daft!

I would add that the initial response from the LABC almost confirmed the potential inconsistency between different BCOs, since I was asked for the address of the property, so that "my enquiry could be forwarded to "the relevant surveyor for my area". I got around that by just telling them of the general area, but the implication seems to be that they accept that different 'surveyors' might give different answers to the same (very 'generic') question!

Kind Regards, John

 

[JohnW2]

... so that still leaves unanswered the question as to what is the difference in the AX110 that makes it 'uniquely' suitable for external use.

A fly screen?
"1.4 AX110: The AX110 incorporates the same features as the AF110, with the exception of the inclusion of an insect/debris grill manufactured from Polypropylene.

Screwfix seem to agree that that is the only difference, since their listing says:

Fitted with environmental mesh to allow external installation.

... which, if that is the only difference, must make it one of the most expensive fly screens around (about £20)

Kind Regards, John

 

[denso13]

... which, if that is the only difference, must make it one of the most expensive fly screens around (about £20)

Your also paying for all the research and development, and new machinery/tooling/sourcing etc.

 

[JohnW2]

Your also paying for all the research and development, and new machinery/tooling/sourcing etc.

Indeed, but one has to wonder how much R&D etc. is necessary to add a fly screen

The more I think about the response I got from the LABC, the more daft does it sound. If, per his advice, I ran the pipe up to a point which was "900 mm above or 3 m away from an opening window", I could save myself about 50 quid by NOT putting an AAV on the top of it !

Kind Regards, John

 

[JohnW2]

The more I think about the response I got from the LABC, the more daft does it sound. If, per his advice, I ran the pipe up to a point which was "900 mm above or 3 m away from an opening window", I could save myself about 50 quid by NOT putting an AAV on the top of it !

I could/should perhaps have added ... even from his point of view (i.e. ignoring financial considerations) his 'advice' seems daft, arguably even 'incorrect'. If the pipe goes high enough to be acceptable as an open vent, then it is surely preferable for it NOT to have an AAV on the top, since that is more 'foolproof' (given that a faulty AAV could 'jam closed', as well as 'jam open'), isn't it ?

Kind Regards, John

 

[denso13]

If the pipe goes high enough to be acceptable as an open vent, then it is surely preferable for it NOT to have an AAV on the top, since that is more 'foolproof' (given that a faulty AAV could 'jam closed', as well as 'jam open'), isn't it ?

Yes, just no need.

I always had a good relationship with LABC and was recommended to some, by them, for issues they thought I could help with.

On the other hand they cost me quite a bit of money on a few projects as they got things completely wrong. Probably just a necessary evil that need to be dealt with.

 

[JohnW2]

Yes, just no need.

Quite so. However, I think you agreed with me that, in the situation I explained, to go with a ('low down'!) external AAV would be the most sensible way to go.

I have responded to the guy pointing all this out - particularly that, having said that an external AAV is acceptable, his 'advice' to have the pipe going up high enough to be left open makes nonsense of putting an AAV on top of it, and I'll yet you know if he has anything to say in reply!

I always had a good relationship with LABC and was recommended to some, by them, for issues they thought I could help with. On the other hand they cost me quite a bit of money on a few projects as they got things completely wrong. Probably just a necessary evil that need to be dealt with.

Indeed. I have no real experience of dealings with such people in relation to plumbing/drainage matters but, in terms of electrical matters, I have come across both types. Most are very reasonable and helpful, but there are some who are simply obsessed with 'rules', and are not prepared (or able!) to exercise any common sense. In the present context, I imagine that such a person would simply say that any external AAV was unacceptable "because Approved Doc H says so".

Kind Regards, John

 

[JohnW2]

Quite so. However, I think you agreed with me that, in the situation I explained, to go with a ('low down'!) external AAV would be the most sensible way to go. .... I have responded to the guy pointing all this out - particularly that, having said that an external AAV is acceptable, his 'advice' to have the pipe going up high enough to be left open makes nonsense of putting an AAV on top of it, and I'll yet you know if he has anything to say in reply!

Just a quick update ...

I've had a couple more exchanges with the guy, but have not really got anywhere useful. In particular, he has not given any sensible explanation as to why he says that an external AAV would be acceptable, but advises that the pipe should go high enough to not need an AAV!

At one stage he suggested that ("if it were easier") a vent pipe could be installed internally, and then up through the roof. I pointed out that such would be very disruptive and aesthetically undesirable, but added that it might be a much more realistic option if one could use a pipe (for the 'dry' part of the run) much smaller than 110mm. In reply to that he merely sent me a page of Approved Doc H, indicating that the minimum acceptable size is 70mm (which, in practice, would, I think, probably have to be 82mm - which is not all that much less than 110mm). I still suspect that engineering considerations would probably allow for a much smaller pipe than that, but he certainly was not buying that idea!

I'm therefore re-visiting the options. An additional one I'm now considering is that of an open vent, routed 'to the side' on a wall of a 2-storey part of the house so as to get it more than 3m from any 3rd-storey windows, in which case it would only have to get 900mm above the 2nd floor windows. One catch with that is that the 2nd floor windows go up very high, nearly to the eaves, so that most of the 900mm would have to be above the eaves, perhaps looking a little silly (and perhaps be a bit 'wobbly'!).

Kind Regards, John

 

[denso13]

I'm therefore re-visiting the options.

I would honestly do what you proposed initially with the low level AAV. It is certified by the manufacturer for that use and would be a justification if anyone picked up on it. Which is highly unlikely to say the least.

 

[JohnW2]

I would honestly do what you proposed initially with the low level AAV. It is certified by the manufacturer for that use and would be a justification if anyone picked up on it. Which is highly unlikely to say the least.

Yes, I have to say that such is my inclination. As you imply, it would seem rather daft to have an 'external AAV' available and not be able to use it as such.

I suppose the only issue is that everyone seems agreed that this approach is only acceptable if there is an open vent in a nearby property - and, even if that is the case today, one couldn't be certain that would always be the case. As for the 'situation today', I confess that I haven't thought of looking very carefully (but will when I'm next at the place, which is quite a long way from my home), but I don't recall having noticed any open vents in the vicinity, so maybe most of the houses have AAVs in their roof spaces? Whilst waiting to get there, I may see if Mr Google's satellite images can tell me anything!

Kind Regards, John

 

[denso13]

Yes, I have to say that such is my inclination.

You don't need LABC involvement to remove a stack and fit an AAV, so you aren't trying to get around any rules. I think in general the rules should be followed and I said so on another recent thread where the OP was trying to do works where LABC should have been involved, but the OP was trying to circumvent it. I don't think that's right.

On the subject of ventilation elsewhere, I don't think it's a deal breaker. If you fit the AAV and it works fine with no abnormal back pressure blowing traps then it will be fine. If there are issues you may have to look at a different solution, but are in no worse off position than when you started.

 

[JohnW2]

You don't need LABC involvement to remove a stack and fit an AAV, so you aren't trying to get around any rules.

I'm not particularly concerned about such matters, but (really for the benefit of others) is that actually true?

As far as I can make out, with the exception of electrical work [which is now covered explicitly in 12.6(A) of the Building Regs],any other 'building work' is 'notifiable' unless it is listed as exempt from that requirement in Schedule 4. In that Schedule, even after amendment, it lists things such as replacement of bathroom items, work on cold water systems and replacement of gutters and rainwater pipes etc., is says nothing about soil pipes or drainage systems and, indeed, qualifies those exemptions with:

..... where the work does not include any work to underground drainage, and includes no work to the hot or cold water system or above ground drainage, which may prejudice the health or safety of any person on completion of the work

Am I misunderstanding?

On the subject of ventilation elsewhere, I don't think it's a deal breaker. If you fit the AAV and it works fine with no abnormal back pressure blowing traps then it will be fine. If there are issues you may have to look at a different solution, but are in no worse off position than when you started.

Again, is that necessarily correct?

As you say, in terms of 'air admittance', the situation is pretty straightforward. It either 'works' or it doesn't (in which case one would re-think) - and I imagine that it very probably would 'work' initially, the issue being that the AAV may theoretically eventually 'get stuck' (resulting in water being 'sucked out' of traps etc.) - but, again, one would then simply review the situation, and either replace the AAV or move to a Plan B, if that situation eventually arose.

However, air admittance is only half of the story. Some people here have 'majored' on the need to allow the release of toxic gases from the drainage system - something which AAVs are specifically designed not to do. That need can obviously only be addressed by open vent(s), in the same or other properties - which is a reason why it would not really surprise me if work on soil pipes etc. were 'notifiable'.

However, having said that, pragmatically I am very inclined to do as I originally suggested, and not lose much sleep over 'rules' or other people's viewpoints!

Kind Regards, John

 

[denso13]

Some people here have 'majored' on the need to allow the release of toxic gases from the drainage system - something which AAVs are specifically designed not to do

Which is what I meant with having issues when installed. You will know if you have a problem with back pressure and will then need to find a different solution.

However, having said that, pragmatically I am very inclined to do as I originally suggested, and not lose much sleep over 'rules' or other people's viewpoints!

With respect you seem to be trying hard to find a reason not to. You don't need LABC and you are using a fitting designed for the purpose intended. Rules or others views don't come into it.

 

[JohnW2]

Which is what I meant with having issues when installed. You will know if you have a problem with back pressure and will then need to find a different solution.

Fair enough. I didn't realise that you were talking about such a magnitude of 'back (positive) pressure' - but is that really likely to arise in the absence of a blockage in the drain or sewer (which would obviously have to be addressed)?

With respect you seem to be trying hard to find a reason not to. You don't need LABC and you are using a fitting designed for the purpose intended. Rules or others views don't come into it.

I may have given that impression, but it's not really the case - I will very probably end up going with my Plan A. It would certainly be the easiest approach but, given that I already have at least some pipe and fittings, it might well not be the cheapest, given the prince of the external AAVs!

However, I came here (and turned to a BCO) for advice, and with one person here expression quite strong opposition to my proposal, and the BCO giving daft advice, I have to at least think about those bits of 'advice'.

You again say "You don't need LABC" but (as I said before, mainly for the benefit of others) I'd be interested to learn what is wrong with the reasoning (interpretation of the Building Regs) I presented in my previous post.

Kind Regards, John