How To Connect Up Radiators


Though technically one of the easier jobs of DIY central heating installation — if you have done any plumbing previously — connecting the radiators to the boiler involves a great amount of upheaval in every room in the house.

Plan the order in which you fix the pipework to the radiators so that you disturb each room for as short a time as possible: it’s probably best to do the most farflung branches first, then work your way back to the boiler.

Start at the radiator end. If the pipes are to run underneath floorboards, lift these first so that you can check on the position of the joists. Don’t try to lift the board closest to the wall the radiator is on (if the boards run parallel to the radiator); it is easier to lift the next one.

Screw the radiator valves hand-tight onto the unions you fitted to the radiator earlier and mark the floorboard directly underneath the other end of the valve. Remove the valves to prevent them from being damaged, and drill holes about 18mm diameter through the floorboards (assuming you are connecting to the radiator with 15mm pipe). Drill smaller holes if you’re using one of the small bore types.

connecting radiators

Replace the valves, this time smearing a little paste on the metal mating surfaces. Then slip a length of pipe through the hole in the floorboard and into the valve to check that all is well and that there is no strain on the valve or the pipework.

You will almost certainly have to change the direction of the pipework under the floorboards from vertical to horizontal at this point. Don’t try to bend the pipe — there isn’t usually enough room under the floorboards for this. Instead, use an elbow fitting. Both compression and capillary fittings are difficult to use in this position unless you assemble them first then wiggle them into position — you may find a push-fit connector is well worth while here.

Again, be prepared to make modifications to the design — especially in the exact pipe runs and the fittings used. Ensure that pipes do not have dips or peaks in their length —this could trap air. All pipes run from boilers to radiators should have a slight constant rise or fall along their length.

Pipes under floorboards

There are various ways you can saw through floorboards to lift them. But whatever you use, take great care: there may be electric cables lying just beneath the surface.

Circular saw: Adjust this to just cut through the thickness of the board — experiment in a concealed corner. Set the saw going before lowering into the board, and stop when you reach adjacent boards. You can cut either to one side of a joist or on top of a joist — on top would be better because it makes it easier to fit above the old joist. Finish off the cut at each side either with a hand saw or (if you have cut over a joist) with a narrow chisel.

Jig saw: You can’t cut over a joist with this, but only to one side, and you have to take even greater care that there are no cables or pipes beneath. Drill whole for the blade on one side and set the saw going before you lower it into the wood. You can cut neatly right up to the adjacent boards.

Flooring saw: This is a hand saw specially shaped so that you can make cuts in a laid floorboard. If you can hire one, it could be a useful tool.

After cutting the end, lift the board by carefully levering under the side with a wide bolster chisel. If the boards are tongued and grooved, you will first have to saw or chisel through the tongue along one side of the full length — avoiding intervening joists — before you can lever the board free.

You will have to cut notches in joists if you want to lay pipes across them. This is easily done by sawing down both sides of the notch, then chiselling out the wood. Take care not to go too deep

say 5mm more than the diameter of the pipe — and make sure the pipe will run along the centre of a floorboard, not close to one edge where you might accidentally nail into it as you refit the board. If possible, have separate notches for each pipe — a single wide notch may weaken the joist.

Lay the pipe in the notch, making sure it is not binding against the sides. Help prevent creaks and noises by packing the notch all round with pieces of insulation material. TIP: Protect the pipe by screwing a metal plate across the notch — chisel a rebate to make the top surface flush.

Leave a Comment