combi boiler airlock

[hoojar]

I'm installing pipework in my home for a combi boiler. I had a plumber out who's willing to let me do the pipe work and then he will inspect it and connect the boiler but he says theres a problem with the layout of my pipes.

Basically, I'm trying to avoid cutting into my concrete floors downstairs so I'm going to use the plastic piping and run it behind kitchen cupboard and skirting board etc but at one point I need to cross a corridor so I was planning on running the pipe up the door frame, across the top of the door and down the other side - luckily the door has voids that enable me to do this. would this cause an airlock or any other problem? Is it not just the same as running the pipe upstairs to other radiators and then back down?

he also had a very low opinion of the plastic piping - apparently it corrodes the system after a few years.... Is plastic piping OK or should I stick with copper?

thanks.

 

[Agile]

Every professional would recommend copper.

Plastic is seen as for cheap jobs and DIY use. Thats why its used in so many new homes.

Taking CH pipe up and over a door will be likely to cause air to congregate at the top an dideally an auto air vent would be fitted.

In practice most air can either be forced out by pressured flow or released from a compression or push fit joints. But it can then collect there later and make water noises.

Tony

 

[hoojar]

Thanks for the reply.

regarding the plastic pipe: this is a cheap DIY job

what sort of issues do you get with the plastic pipe compared to copper?

regarding the air block: is an auto air vent a cheap item? and also does this problem occur when taking the pipes upstairs to connect to the radiators? do I need to put an auto air vent anywhere else?

 

[hammerswinger]

Hi,
I think your plumber is wise to advise you that the pipework around the door isn't a good idea.

As Tony advised you will more than likely end up with a build up of air that is always present in the lengths of pipe that cross the top of the door frame. This is where you would need to fit an auto air vent but this isn't really practical if you are trying to hide the pipes...forget the pipes around the door frame, its a none starter in my opinion.

When Houses have concrete ground floors the downstairs rads are normally fed with drops from the floor above, depending on the size of pipe used / size of rads one drop could feed a single rad or maybe a couple depending on where the rads are situated etc.

Can you not drop the pipes for this rad from above?

Yes you get air in the pipes dropping from above, but it will eventually be pushed into the rad where you can bleed it off or it will rise up the pipes to the upstairs circuit where it will be pushed into a rad.
You could put an auto air vent at the top of each drop of pipe but each one of these is a point where the system could leak so in real life they are not always fitted!

Copper V's Plastic...

Copper is preferred by some, Plastic by others, I guess its each to their own, they will both work & give years of trouble free service so I wouldn't worry too much about your choice.


Cheers.

 

[hoojar]

thanks for the reply.

Now I'm thinking I go straight upstairs directly from the boiler (I don't have much choice about the position of the boiler so that can't go upstairs to start with) where I install an auto air vent. then loop round all the upstairs radiators and at some point drop down past the problem doorframe and concrete floor and loop round the rest of the radiators with an auto air vent at this drop.

does that sound correct?

I think my problem has been trying to do the downstairs before upstairs simply because thats where the boiler will be...

 

[hoojar]

one other question. are conex fittings ok for use in central heating pipes?

I'm planning on mainly using the plastic pipes but a couple of runs will be copper.

 

[hammerswinger]

Everything depends on the layout of your house & the convenient points to drop pipes & position rads.

Yes you can take the 22mm pipes up from the boiler straight upstairs to feed the upstairs circuit & then drop down to the rads downstairs one at a time.
The pipe runs upstairs will have to be thought about & sized correctly depending once again on the layout.

If you have a cupboard downstairs maybe you could bring pipes down in this then drill through the wall to feed a rad...you get the idea.

If possible it's best to drop down in the corner of the room as the pipes can then be boxed in & you hardly notice them.

I don't have a lot of experiance of auto air vent other than the ones fitted to combi boilers but I would imagine that you would fit them to the top of the vertical pipes from the boiler, I'm sure someone that has used them will comment.

Compression fittings are ok but if its copper to copper you would be better off with solder fittings.
If you are using compression fittings on the plastic pipe make sure to use the insert.


Cheers.