Yet another condensate question

[mike42]

Having read a dozen threads here an elsewhere I'm still none the wiser as to what the preferred method of routing condensate from a boiler is. Apart from calling a pro that is. The current arrangement is not satisfactory.

Boiler is in an integral garage. Other side of the wall 2 metres along is a downpipe into a mixed rainwater/sewer.

OUTSIDE:
A single steep run of 32mm rigid pipe flowing into a hopper to achieve air gap and clad with armour flex, K-flex or similar. I think I'm good there?

INSIDE:
The boiler comes with a roughly 500mm length of flexi pipe leading from the condensate trap. It is considerably narrower than 32mm. So what to do? A washing machine trap with an upstand done in 32mm that I can stuff the flexi into? I read somewhere an internal air gap isn't allowed. I'm totally confused - surely there is a standard way of doing this ?

 

[mike42]

Well, I think I can answer my own question in case anyone else would find this useful. Pretty detailed steps there although must admit I don't really know how important these guidelines are but assume if you comply with them you comply with the relevant building regs. I will obviously check the MIs for my boiler just in case there are any differences.

https://www.hhic.org.uk/uploads/5FF598A848C3F.pdf

 

[ericmark]

Interesting, I did a word search for "contaminated" no hits. Clearly condensate can be plain water, this is what we get from any heat pump, it is reasonably pure, great for using in the steam iron, I know I save some of mine in the summer for used with the steam iron and press.

But condensate from a oil or gas boiler may have contaminates in it, and these may be acidic, so we don't want them in any pipe work which may be reduced into salts as a result of the acid.

What is important is to know what is in the fuel which can be turned into acid, sulphur is clearly a problem. I know with motor vehicles we were very concerned about sulphur in the fuel, are we used special oils to absorb the sulphur. Specially with diesel engines. In the main drains today are plastic, but any iron pipe work would have a problem, same with any other metal like copper. Not so sure about lead, I thing we need a voltage to get a lead acid battery?

I will monitor answers out of general interest.

 

[Mister Banks]

The condensate on my gas boiler has just been routed into an open vertical pipe (just like you get for a washing machine) with a trap at the bottom, this then flows into the waste pipe that runs under the side footpath.

 

[mike42]

The condensate on my gas boiler has just been routed into an open vertical pipe (just like you get for a washing machine) with a trap at the bottom, this then flows into the waste pipe that runs under the side footpath.

Interesting thanks. Presumably your boiler doesn't have a built in trap with at least 75mm depth then because according to the Water Regs doc I posted, it says you don't need a trap in that case.

Then again if there is no trap external to the boiler, wouldn't you get smells or at least drafts from a pipe routed outside so maybe a trap soon after the boiler is better to have than not even if its not strictly required ?

 

[Madrab]

The guide explains most if it, so it's a good one to follow.

Condensate is slightly acidic therefore it can be run into a downpipe or soil pipe - as long as that pipe is an actively used wet section, especially if it is cast iron. Normal routes would be to a gutter downpipe or the wet section of a soil pipe or any other used section of waste pipe. Most if not all boilers these days have a compliant internal trap, some are syphonic some are just normal water seal traps so a trap further downstream (edit) wouldn't be needed. One fail a lot fall into though is running the condensate into an un-trapped section of internal waste, that can lead to sewer smells emanating from the air gap/tundish section, this can be overcome by using a TUN5 but this needs to be in a serviceable location

The golden rule if running externally is always increase the condensate pipe by 1 pipe size (>32mm) before it enters the wall, not at the exit. This is to avoid freezing. Externally it can be insulated yes but this is normally a belt 'n' braces approach unless it is in a location that is known for regular and extended periods of sub zero temps.

 

[Mister Banks]

Interesting thanks. Presumably your boiler doesn't have a built in trap with at least 75mm depth then because according to the Water Regs doc I posted, it says you don't need a trap in that case.

Then again if there is no trap external to the boiler, wouldn't you get smells or at least drafts from a pipe routed outside so maybe a trap soon after the boiler is better to have than not even if its not strictly required ?

My boiler does have a built in trap, the drainpipe was pre-existing so the installers just used it for convenience.

 

[mike42]

The guide explains most if it, so it's a good one to follow.

Condensate is slightly acidic therefore it can be run into a downpipe or soil pipe - as long as that pipe is an actively used wet section, especially if it is cast iron. Normal routes would be to a gutter downpipe or the wet section of a soil pipe or any other used section of waste pipe. Most if not all boilers these days have a compliant internal trap, some are syphonic some are just normal water seal traps so a trap further downstream (edit) wouldn't be needed. One fail a lot fall into though is running the condensate into an un-trapped section of internal waste, that can lead to sewer smells emanating from the air gap/tundish section, this can be overcome by using a TUN5 but this needs to be in a serviceable location

The golden rule if running externally is always increase the condensate pipe by 1 pipe size (>32mm) before it enters the wall, not at the exit. This is to avoid freezing. Externally it can be insulated yes but this is normally a belt 'n' braces approach unless it is in a location that is known for regular and extended periods of sub zero temps.

Thanks - a good mini-guide right there.

Would you make the hole in the wall large enough for both 32mm pipe _and_ 13mm or 19mm insulation? That'd be quite a big hole just to accomodate a few drips ?

 

[Madrab]

Nope - I wouldn't see the need to insulate within the wall, 35mm hole and seal from the outside, could use some synthetic insulation and it should be fine, then just insulate from the outside.