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By Mozziebear
Hi all,
I have just joined this forum and this is my first post. A little bit about myself then I will cut to it.
I have been a builder, painter and decorator for the past 30 years. In the past I have been involved in fairly substantial builds but now, as much more of me aches, I tend to do a lot easier and smaller stuff. Typically, refurbishments, kitchen and bathroom installations along with the plastering, tiling and most of the associated electrical and plumbing works.
So, I could really do with some advice and technical help regarding the installation of a new boiler and its condensate pipe by a plumber/builder as part of a kitchen installation that I undertook.
My issue is with the way in which the condensate pipe has been installed. Initially it came out of the wall in 22mm and was uninsulated. After a lot of grief I managed to get the plumber to change the pipe to that which a Vaillant engineer said it should be – min 32mm - the engineer also said it should be insulated with proper external grade insulation; bit of a no brainer that as clearly any external pipework affected by the weather should be insulated.
The plumber changed the pipe by cutting the 22mm at the elbow where it comes out of the wall and ran the rest in 32 mm as well as leaving it uninsulated. He refuses to insulate it as well as change the 22mm pipe and elbow to ensure that all external pipe work is 32mm including what comes through the wall.
Vaillant installation instructions sort of cover the insulation but they also refer to BS6798 2014, which is something I cannot access. Can anybody give me the parts of this BS that refer to these two issues as I would like to know if I am barking up the wrong tree.
I welcome any and all help and advice that you have to offer.
Thanking you all in advance.
User avatar
the regs and manufaturer states the condesate should be internally connected where possible. however, this cant always be pratical.
when i run a condensate outside, i go through with 21.5mm o/flo then if its north facing(40mm)-32mm elbow which acts as a air break, then 32mm run to drain (i dont bother insulating either).
i dont see the installer is necessary doing anything wrong there as long as the pipe diameter is upgraded to 32-40mm. all depends whats paid for really! any freezing of candense tends to happen once every 5 years anyhow. this last winter i had 6'' lengths of 40mm freeze so theres no garentee. its also a fact that pipe insulation freezes when wet and reverses the purpose of it in the first place in turn freezing the condense.

i will see if i can find the bs for you.
User avatar
quoting bs6798/14

From current BS 6798:2014

Specification for selection, installation, inspection, commissioning, servicing and maintenance of gas‑fired boilers of rated input not exceeding 70 kW net Separate pressure relief valve and condensate discharge pipes
. Diameter of internally run condensate pipe
The condensate drainage pipe connected to the condensate drain outlet on the boiler shall have a minimum internal diameter (ID) of 19 mm, or as recommended by the boiler manufacturer, to promote the clearance of condensate.

Historically, the outside diameter (OD) has been used to specify the size of condensate pipe required as this automatically delivered the internal diameter (ID) considered necessary to aid efficient disposal of the condensate. With the advent of European
Standards, plastic pipe manufacturers can now choose to manufacture to a variety of ODs and wall thicknesses, yet the minimum ID requirement to aid efficient disposal of the condensate remains. Hence the minimum ID is now specified as the requirement,
providing the maximum flexibility of choice for the installer. Diameter of externally run condensate pipe
Any external condensate drainage pipe shall be increased to a minimum of 30 mm ID to reduce the risk of freezing.

When a boiler is to be installed in an unheated location, e.g. a loft, basement or garage, all condensate drainage pipes downstream from the trap or siphon should be considered as external.

Annex A

A.2 Connection to an external foul water discharge point
A.2.1 General
Where an external foul water discharge point is used the following measures shall be adopted.
a) The pipe shall be run internally within the building as far as possible before going external. Where the discharge pipe is external to the building the pipe diameter shall be increased to a minimum of 30 mm ID before it passes through the wall. Wherever practicable, for condensate discharge pipe operating under gravity, the fall to the horizontal for the 30 mm ID pipe through the wall shall be greater than the 2.5° required for internal 19 mm ID pipe.
b) The external run shall be kept as short as possible, preferably less than 3 m, taking the most direct and most vertical route possible to the discharge point, with no horizontal sections in which the condensate might collect.
c) The use of fittings, elbows, etc., shall be kept to a minimum and any internal burrs on cut pipework shall be removed to ensure that the internal pipe section is as smooth as possible.
d) To minimize wind chill at the open end of the condensate drainage pipe, the end of the pipe shall:
1) terminate below the grating and above the water level; and
2) be covered by a drain cover such as those used to prevent blockage by leaves.
e) To improve drainage the end of the pipe shall be cut at 45°.
f) The pipe shall be insulated from the point at which it emerges from the outside of the external wall of the building (ensuring no gaps between insulation and wall) using suitable waterproof and weatherproof insulation, e.g. Class O with a suitable PVC or other UV protective coating.
g) The owner of the appliance shall be advised that this type of installation is more likely to freeze in prolonged periods of extremely cold weather (see 6.3.4), resulting in boiler shutdown requiring remedial action.
h) Where there are likely to be extremes of temperature or wind chill, the use of proprietary trace heating systems incorporating an external frost thermostat can be considered, ensuring that the installation instructions of the trace heating manufacturer are followed.
Other cold weather protection methods that are endorsed by the specific boiler manufacturer and/or specific service organizations can be adopted if the method adopted is acceptable to the owner of the appliance, e.g. innovations such as preheating condensate before it leaves the thermal envelope of the dwelling, and blowing warm air down the condensate pipe.
Class O insulation is not UV stable and therefore subject to deterioration when exposed to sunlight. PVC coated versions are UV stable and have added mechanical strength.

since the last bad winters previous-2014 on, vaillant installation refers to the above document for the correcct condense installation.
By Mozziebear
Thanks so much for that I really appreciate it.
With regard to the insulation I understand that the foam internal stuff would be inadequate and indeed would work against you once wet but can the same be said about the proper external PVC coated stuff that is referred to ?
Also, A.2.1a. states that the pipe should be 30 mm before it passes through the wall, which mine isn't and nor is the finishing of the pipe inside the grate etc.
I know this sounds really picky but I would not be exploring these avenues regarding this pipework if the installer had been more helpful, communicative and professional in the first place; this is how he has got me!!!
In all my years in the building trade the best people I have worked with and for have been the ones that deal with any problems or issues that arise from a job in a professional manner even if sometimes its you that has to take the hit; someone who puts their hands up when wrong or works with you to find an acceptable solution rather than just pretend you don't exist. Sorry about the rant............I'll shut up now.
So, my question would be, if installation instructions refer to this BS and the work has not been completed to this standard, can he tell me to do one or is he duty bound to comply with it.
All the best

By joni os
Mozziebear wrote:
May 17th, 2018, 6:05 pm

So, my question would be, if installation instructions refer to this BS and the work has not been completed to this standard, can he tell me to do one or is he duty bound to comply with it.
All the best

Your years in the building trade will have taught that if esoteric elements of BS are going to cost the client money they will often be ignored whilst if looking for an excuse to delay or reduce payment to contractor the same elements will be deemed essential for performance of the contract.
Many households have a drop in excess of 1mbar between meter and appliance when all appliances operate at maximum demand but would be aghast if forced to pay cost of upgrade. When watching utilities backfilling their own services, selected fine material adjacent to service often appears to be an aspiration rather than a commitment.
Outside taps lacking internal check and iso valves; Patios less than 150 mm below DPC. Fencing without mowing strip, the list is endless.
Without knowledge of what was agreed at the time you awarded the work it is not possible to pass judgement but bear in mind the principles of "Contra Proferentem"; "Quantum Meruit"; and "Proportionality", in ongoing discussion with your installer.
User avatar
So, my question would be, if installation instructions refer to this BS and the work has not been completed to this standard, can he tell me to do one or is he duty bound to comply with it.
All the best.

most of the time i go through wall in 21.5mm as its less intrusive if on view, however if customer was complaining whilst on site then i would change it so i get paid............
two things here,
1. if hes not been paid in full then you can request it done, but..
2. the get out to an extent is 'where praticaly possible B.S must be adhered to' is the get out clause if its a minor issue.

that then brings J-o post into context especially on new builds that i see where some work beggers belief of corner cuts.

as long as the external pipe is upgraded to 30 or 40 (and even 30 inside 40 to insulate) i doubt it will be an issue, and no, he could tell you to do one as it wont be challenged by anyone else other than you.

By Mozziebear
Thanks to all for replying I do really appreciate the time and info you have given me.
I am quite dismayed that the BS standards are not something that I can use to get him back, no wonder he dismissed them when I mentioned them to him a while back.
The way I have approached work is clearly different to him as If it was me, the pipe would be finished correctly at the drain and properly insulated as a matter of course if for no other reason than to avoid ANY comebacks or repercussions.
He was paid when the job was completed as unfortunately this issue did not surface until some months later. It really irks me that I am gonna have to use my hard earned to put right/finish his job.
Thanks again everyone and good luck in the future.
By joni os
How did the issue surface some months later? If the condense froze in the pipe,water backed up and boiler cut out then it would be reasonable to carry out work to ensure it would not happen in future. Much depends on where you live in UK. What might be overkill on a south facing wall in Cornwall would be prudent on a north facing wall in Halifax. In my own area I attended a number of boilers this year with frozen condensate. The solution being to detach the flexible as it leaves the boiler, place pan underneath to collect water until temp rises,(one or two days) and reconnect.
To date no one has paid for me to upgrade their pipework and provided the 21.5 goes into 32mm external I would not criticise the original installer. Now that the householders know what to do, just like putting pressure in system, I expect no call backs.
By Mozziebear
The condense pipe froze shutting the boiler down. As the boiler had been working up to that point I called Vaillant assuming it was a boiler issue. He boiled a kettle unfroze the 20mm uninsulated external pipe and charged me £90. The engineer told me, as did a BG engineer that I know, that the external pipe should have been minimum 30mm and insulated, something I was unaware of when the boiler was installed in better weather.
If he had done his job properly to start with, ie work to finishing a job in conjunction with BS6798 and the installers instructions, the 88 year old lady would not have been without heat for a couple of days n I would not be out of pocket.
It has been a battle to get him to change the external pipe, something that he did not do happily and to my mind deliberately left it uninsulated just to make a point. If you have to come back to do something why do it badly if not just to pee the customer off and why would anybody leave a pipe vulnerable to freezing uninsulated if not just to be bloody minded?
He cut the corners n I have to suffer. Not happy

By joni os
Understand your frustration in paying £90 for a bogey warranty call. Certainly pass cost to installer, although I suspect his response will be," Why didn't you call him first".
On the plus side, stick with this forum and you will read lots of useful information to avoid such problems in the future. Provided it is not GAS WORK there is much you can do to ensure the continuing comfort your 88 yr old tenant. Vailliant are good boilers and my recent experience of their service engineers has been equally good. When it has been a warranty issue the £90 upfront payment has always been promptly refunded. Keep your annual services up to date,not just the landlord's certs.
Keep posting other queries, and a belated welcome to the forum.
User avatar
as for the 21.5mm run outside, yes, it would be reasonable to get the installer to put right on call out. as i would if i had installed incorrectly expect to do it 'for free'.
like i said before though, i had 40mm pipes freeze from condense, bath waste and even 80mm drain-pipes. insulation will only hold it off a bit longer until the temp drops enough.
the only way to ensure it DOES NOT FREEZE is by installing trace heater and thats more£ on the job.

is the boiler in a garage?
User avatar
Mozziebear wrote:
May 20th, 2018, 2:03 pm
No the boiler is in the kitchen and vents out the wall to the external drain as the house is a semi.
Not familiar with trace heaters but I am assuming a small heating element of some description for cold weather ? Expensive? Worth the effort?
price depends on the length but cheap as chips on ebay about £40 for 4meter. easy to install and length of cable pushed down pipe or tiewrap external and insulate over.
By joni os
Called on Saturday. Viessmann boiler not working, showing F4 fault code,"Frozen Condensate". Problem debris in collection bowl. Knowing boiler,doing basic checks and having regular service saves much grief and inconvenience.
The Vailliant manual will recommend a shock arrester between boiler and incoming cold water main when non return valve is present. Most water meters include non return valve. The OP may wish to check if his system is compliant.

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