Replacing central heating pipework and radiators

paperclap

Hi all,

So, I've a few questions...

Please bare with me, as I'm relatively new to plumbing!

The below is all from the mindset of wanting to drain down my central heating system, replace the exiting viewable pipework (in order to have higher skirting boards) and replace the radiators to type 21 radiators (we've old single panel rads).

—

Is our central heating system unvented (pressurised) or vented?

We've a conventional boiler, a large cold water tank in the loft, an airing cupboard (with a hot water cylinder). Looking on the outside of the property, we've also an overflow pipe – which presumably, would insinuate a feed and expansion tank in the loft for the central heating. I've not seen one, but not gone out of my way to look either. However, we've a filling loop and pressure gauge in the airing cupboard. Is it possible that the system was once vented (feed and expansion, overflow pipe, etc), but has now been converted over to an unvented (pressurised) system (filling loop, pressure gauge)?

—

Going on the basis that our central heating system is unvented (pressurised), is it possible to have an unvented (pressurised) central heating system and vented hot water system simultaneously? If so, do we have this setup?

This is somewhat intertwined with the previous question. Based on the fact we've a cold water tank in the loft, I presume this means we've a vented hot water cylinder? If so, would this potentially mean what I thought was the "old" overflow pipe (for the central heating) is actually the still-in-use overflow pipe for the hot water system (coming off the cold water tank in the loft)?

—

Potential issue with radiator in conservatory?

We've got a double panel double convector radiator in our conservatory which I am not replacing. I'm also not planning on touching the pipework running up to this rad. The pipework is tee'd off the current pipework (from in the house), and is on the same level. When I plan on replacing and moving up the new pipework in the house, will this pipework and radiator be an issue? As, it will effectively be below the rest of the other pipework. It doesn't have a drain-off valve, should I ever need to isolate and drain. I could add one, but hadn't planned too.

—

Are drop-down legs on all radiators better?

Our current system has two drop-down legs. The first drop-down leg is in bedroom 1 – this tees off one way to the bedroom 1 rad and then the other way to the hallway. The second drop-down leg is in bedroom 2 – this tees off one way to bedroom 2 rad, and then the other way it tees off again... one to the living room and the other way to the conservatory. When replacing and raising the pipework, is it worth thinking about adding drop-down legs for every single radiator, or is the current setup best? Are there any benefits to all rads having drop-down legs?

—

Thank you in advance!

Jeepers_Creepers

Hi Laurence.

You have a filling loop and a pressure gauge in your airing cupboard? Does the gauge actually have a reading on it - say around 1 bar? Have you ever had to top it up?!

That gauge and loop would suggest a pressurised/unvented boiler, which is known as a 'system' boiler. It's possible that this same boiler originally was 'vented' and had a small F&E tank in the loft which was removed, the system sealed and pressurised, but for this I would also expect to see an expansion vessel somewhere on that system - and the airing cupboard would be the obvious place for this. Since there doesn't appear to be an EV on your system, then I suspect your boiler is actually a 'proper' 'system' boiler with a built-in EV, so never had an F&E tank in t'loft.

What make and model is it?

So, your boiler/radiator/hot cylinder heating loop is also 'system'/unvented/pressurised and has no small F&E tank. Your DHW (domestic hot water) on the other hand is vented, and is supplied by the large CWS (cold water storage) tank in the loft. I suspect the overflow pipe is for this - it would need one.

It's totally possible, then, for you to have an unvented boiler and a vented hot water system - and that, almost certainly, is what you do have.

I see no issue with the connie rad - just keep it plumbed as it currently is. It doesn't matter if a pipe goes lower at any point - it'll still work. Yes, it is desirable to have the drain-off point at the lowest point in your system, but if it isn't, then all it means is that there will still be some water left sitting in that lower pipe - not a biggie.

What's a drop-down leg? Is it a rad pipe that goes to the top corner of a rad, or is it a pipe that drops down from the ceiling? If the former, then with modern new rads, I'd stick with conventional connections at the bottom-opposite ends of the rad - it just looks neater. I understand that rads - some at least - do work a bit better with diagonally-opposite connections, but this is old hat now and just not needed.

So, your plan is to remove all the old rads, extend the pipe tails coming up from the floor - and move them away from the wall by around a half-inch or so to suit the new, deeper rads? That's fine. Who's doing this - you or a plumber? Will they/you be lifting a floorboard at each rad in order to connect this new tail below floor level where the join will be hidden?

FreeBear

laurencewhymark said: Are drop-down legs on all radiators better?

I have just two drop down legs for the radiators on the ground floor here. One leg feeds a radiator in the lounge and the one in the hallway. The other leg is for the kitchen & dining room. As long as you limit the number of radiators hanging off each leg to a maximum of three, there is not really any problem. It saves on the amount of copper pipe used and reduces the amount of fuggly pipes on show. There will also be a very slight reduction in the volume of water the boiler needs to heat up, but that is pretty academic when compared to the total volume of water in the system.

southcoastrgi

Pictures speak volumes 

paperclap

Jeepers_Creepers said:

Hi Laurence.

You have a filling loop and a pressure gauge in your airing cupboard? Does the gauge actually have a reading on it - say around 1 bar? Have you ever had to top it up?!

Yes, I've used it to fill up and repressurise (to 1 bar) before (after bleeding a radiator).

Jeepers_Creepers said:

So, your boiler/radiator/hot cylinder heating loop is also 'system'/unvented/pressurised and has no small F&E tank. Your DHW (domestic hot water) on the other hand is vented, and is supplied by the large CWS (cold water storage) tank in the loft. I suspect the overflow pipe is for this - it would need one.

Thanks! I thought as such

Jeepers_Creepers said:

What's a drop-down leg? Is it a rad pipe that goes to the top corner of a rad, or is it a pipe that drops down from the ceiling?

Yes, it's the vertical pipes that come down from the ceiling.

Jeepers_Creepers said:

So, your plan is to remove all the old rads, extend the pipe tails coming up from the floor - and move them away from the wall by around a half-inch or so to suit the new, deeper rads? That's fine. Who's doing this - you or a plumber? Will they/you be lifting a floorboard at each rad in order to connect this new tail below floor level where the join will be hidden?

We're in a bungalow with a concrete floor. All the pipework is exposed and comes down from the loft. I'll be doing it all myself.

FreeBear said:

laurencewhymark said: Are drop-down legs on all radiators better?

I have just two drop down legs for the radiators on the ground floor here. One leg feeds a radiator in the lounge and the one in the hallway. The other leg is for the kitchen & dining room. As long as you limit the number of radiators hanging off each leg to a maximum of three, there is not really any problem. It saves on the amount of copper pipe used and reduces the amount of fuggly pipes on show. There will also be a very slight reduction in the volume of water the boiler needs to heat up, but that is pretty academic when compared to the total volume of water in the system.

Maybe not a massive difference as you say... but is it worth considering, since I'm going to the trouble of replacing the pipework anyway? That said, therein lies the challenge of cutting into the main pipes (in the loft), and finding a suitable place for those drop-down legs!

FreeBear

Plan your plumbing to reduce the total amount of pipe used. In a well insulated house with decent double glazed windows, there is no need to put the radiators under the windows. Instead, site them on an internal wall to keep the pipe runs short.

The fewer pipes you have, the less joints that need to be made - That saves money on fittings and reduces the points that might leak.

Tip - If you are soldering the joints, wipe each one down with a damp cloth. Mix some bicarbonate of soda in to the water, and it will help to neutralise the acid flux.

paperclap

There's no inherent need to put radiators under windows... but it does seem the most convenient place for them, purely because other furniture won't go there (most of the time).

However, that has raised another question regarding the location of the radiator in our living room. The current rad is directly behind the sofa, which isn't necessarily perfect. With the type 21 rads, given that the heat will disperse out the top, will this location be okay? Or, do you think it would be more beneficial to sit on the other side of the room (would then need a new drop-down leg)?

Regarding the damp cloth after soldering joints... do you mean directly after, or about 30 seconds after the joint has cooled? I've heard if you wipe away the excess flux directly after, you run the risk of cracking the solder due to the rapid change in temperature.

FreeBear

laurencewhymark said: Regarding the damp cloth after soldering joints... do you mean directly after, or about 30 seconds after the joint has cooled? I've heard if you wipe away the excess flux directly after, you run the risk of cracking the solder due to the rapid change in temperature.

Leave the joint to cool down a bit - Give it a couple of minutes as copper can store quite a bit of heat.

Jeepers_Creepers

laurencewhymark said:

Yes, it's the vertical pipes that come down from the ceiling.
Maybe not a massive difference as you say... but is it worth considering, since I'm going to the trouble of replacing the pipework anyway? That said, therein lies the challenge of cutting into the main pipes (in the loft), and finding a suitable place for those drop-down legs!

I wouldn't plumb the rads diagonally, simply because I think it's ugly :-) I doubt it'd make a significant difference anyway, certainly nothing compared to your up-sizing of the rads in any case - a good move, as you'll be able to run them cooler for the same heat output as the previous rads = more efficiency from modern boilers.

So, these 'drop down legs' consist of two pipes for each rad, as would be expected - a flow and a return? Are you planning to hide/box/bury these to hide them? There are ways to do this.

southcoastrgi

laurencewhymark said:

However, that has raised another question regarding the location of the radiator in our living room. The current rad is directly behind the sofa, which isn't necessarily perfect. With the type 21 rads, given that the heat will disperse out the top, will this location be okay? 

They are called radiators for a reason, heat radiates off of them so anything you put close in front will effect the room temperature especially something like a sofa that will soak it up, they are also known as convection radiators which work best with airflow so again your sofa will prevent that working as well as it should

paperclap

Jeepers_Creepers said:

laurencewhymark said:

Yes, it's the vertical pipes that come down from the ceiling.
Maybe not a massive difference as you say... but is it worth considering, since I'm going to the trouble of replacing the pipework anyway? That said, therein lies the challenge of cutting into the main pipes (in the loft), and finding a suitable place for those drop-down legs!

I wouldn't plumb the rads diagonally, simply because I think it's ugly :-) I doubt it'd make a significant difference anyway, certainly nothing compared to your up-sizing of the rads in any case - a good move, as you'll be able to run them cooler for the same heat output as the previous rads = more efficiency from modern boilers.

So, these 'drop down legs' consist of two pipes for each rad, as would be expected - a flow and a return? Are you planning to hide/box/bury these to hide them? There are ways to do this.

Haha, I'd have to agree! I don't think diagonal pipes would look all that great

Yeah, the drop down legs have a flow and return. And absolutely, I am planning to box them in with battens and plasterboard