Insulating Central Heating Pipes and Tanks

Insulating cold water supply pipes and storage tanks is a vital precaution against winter freeze-ups. But on hot pipes and the hot water cylinder, insulation can play another, equally important role — by keeping valuable heat sealed in and cutting down on fuel bills.


insulating central heating pipes and tanksWhat to insulate

♦ Top priority must go to pipes and tanks in the roof space, particularly if loft insulation has already been laid between the joists. This has the effect of lowering the temperature in the roof space, increasing its vulnerability to frost.

As well as the cold water storage tank and supply pipes, don’t overlook the central heating feed and expansion tank, and the overflow pipes running from both tanks to the eaves. (Ice plugs here can easily-cause ballvalve failures to pass unnoticed until it’s too late.)

Next on the list are pipes passing through a cellar, garage, outhouse, utility room or non-centrally heated extension. These may survive cold snaps quite happily while the rest of the house is fully heated (ironically, the escaping heat protects them). Yet it only takes one severe frost while the family is away to create complete havoc.

♦ Check boxed-in pipes. If these run along cold walls, the boxing will insulate them from warmth in the house but not from cold outside.

♦ Finally, check the hot water system. Hot pipes which pass through rooms can be left, as the heat they give out won’t be wasted. But the hot water cylinder and any pipes inside cupboards are prime candidates for insulation — you can save around 75% of heat this way.

The instructions for insulating pipes and tanks (below) give suitable insulating materials for each location, so check before you buy. In some places you may be able to use up any materials left over from insulating the loft.


Trade Tip 1

Is your house safe?

"Even if your pipes and tanks are already insulated, it pays not to be too complacent. Older insulation materials aren’t particularly robust, and in time they have a habit of disintegrating or slipping off (especially in areas where repairs have been carried out).

It’s also possible that whoever installed the insulation skimped on the job. Sadly, we’ve had plenty of customers over the years who thought they were safe from freeze-ups — but weren’t."


Protect pipes with sleeve, or pipe-wrap insulation. Each has its pros and cons, and it’s often best to use a combination of both.


Using sleeve insulation

Insulating sleeve comes in two materials — plastic foam and felt.

Foam sleeve takes the form of rigid or semi-rigid tubes which come in various lengths, and in sizes to suit 15mm, 22mm and 28mm pipes. The tubes are slit lengthways — allowing them to be slipped over pipes — and either clip shut or are fixed with tape or wire depending on the make.

Foam sleeve is the most costly form of pipe insulation, but also the easiest to fit. To estimate, measure each pipe end to end (this covers wastage at joints) and total the figures. Round upwards to the nearest multiple of the sleeve length.

Make a note of any stopcocks, valves or other fittings. Some makes include special two-piece sleeve sections for these; otherwise, insulate them with pipe-wrap.

Felt sleeve is cheaper than foam and comes in rolls around 20m (22yd) long to suit 15mm and 22mm pipes. Although designed to be slipped over pipes before they are installed, it can be fitted to existing pipes by slicing open the stitched seams, then tying or taping in place.

Other materials: Suitable adhesive tape (see Trade Tip 2 below), garden tie wire.

Tools checklist: Sharp knife, mitre box, tape measure, pliers.

1. To fit foam sleeve insulation, prise the lengths apart and slip them over the pipe. On the non-moulded type, cover the split lengthways with tape.

using sleeve insulation

2. Tape lengths together where they butt-join. At corners, it’s neater to mitre the ends in a mitre box — use a sharp kitchen knife to cut the sleeve.

3. Cut notches in the sleeve to clear stopcocks and other fittings (see also Problem Solver below). Where necessary, add an extra layer of pipe-wrap.



Insulate boxed-in pipes with loose fill loft insulation, which comes in bags of various sizes. Mineral wool loose fill is easier to handle than the granule type, but wear gloves — the fibres irritate the skin.

Open up the boxing at places which give good access to the entire pipe run, then push in the loose fill. Use an opened out wire coat-hanger for this part of the job, and channel the material through a home-made cardboard tube. Distribute it evenly over the pipes until they are completely covered.


Using pipe-wrap

Pipe-wrap (also called bandage) comes in rolls in a variety of materials, including felt, mineral wool and glass fibre. Some makes have a plastic or metal foil backing; others are self-adhesive, which makes fitting easier. Rolls are typically 50mm or 75mm (2-3") wide and 5m (16.5") or 10m (33′) long. Make sure you compare like with like when checking prices.

Pipe-wrap is simply rolled around the pipes, overlapping on each turn. It is particularly useful on runs full of bends or joints, and for insulating stopcocks and valves.

Coverage is around half a metre of pipe per metre of roll, but treat this as a rough guide and err on the generous side — your supplier should be prepared to take back unused rolls if they’re unopened.

Clean the pipes with a damp cloth before fitting self-adhesive pipe-wrap. For other types, cut lengths of wire to secure the ends.

Blanket roll left over from the loft can be used instead of pipe-wrap providing it is at least 50mm (2") thick. Cut the roll into 75mm (3") ‘slices’ using a panel saw. Then fix the home-made bandage in place with twists of wire or plastic tape.

Tools checklist: Trimming knife, panel saw (for blanket roll).

Other materials: Stiff wire or suitable adhesive tape (see Trade Tip 2 below).


Trade Tip 2

"At a pinch, you can use virtually any type of self-adhesive tape to secure foam sleeve, pipe-wrap and polystyrene slabs — but some types are better than others. Some insulation manufacturers include purpose-made glass fibre reinforced or PVC tape as part of their ranges. A good alternative is 50mm (2") plastic parcel tape, sold by stationers. Don’t use insulating tape, as it tends to lose its adhesion."


1. To fit pipe-wrap, start with a double turn and secure with a twist of garden tie-wire. Wind it around the pipe in a spiral, overlapping 1/3 of its width.

to fit pipe wrap ...

2. Allow a double overlap where lengths join. Secure the non-adhesive type with wire or tape —but not too tightly, or you’ll reduce its effectiveness.

3. Wrap stopcocks and valves in an ‘X’ pattern so that the body of the fitting is completely covered, leaving only the handle exposed.



Insulating jackets, consisting of quilted plastic sections filled with mineral or glass fibre wool, are available to fit all common sizes of cylinder. The sections are linked via a wire collar fitted around the topmost pipe, and held in place with elastic or adjustable straps. You’ll find it easier to assemble the jacket if you fit the straps first.

If there is an immersion heater fitted, arrange for it to coincide with a joint between sections and leave the cap exposed. The same applies to a cylinder thermostat.

1. Fit the jacket’s straps loosely around the cylinder, a quarter of the way from the top and bottom. Then thread the jacket sections through the wire collar.

insulating the hot cylinder

2. Fit the collar around the top pipe and drape the sections over the cylinder. Tuck the sections under the straps, one by one closing any gaps as you go.



If you have the choice, insulate tanks after the pipework so that the vulnerable connections are doubly protected. Leave the area below a tank free of insulation to take advantage of rising heat.

a properly insulated cold storage tank

Tank insulation kits consist of specially tailored slabs of polystyrene foam, plus tape or straps to secure them. They are made to fit all common sizes of plastic tank, but are unsuitable for round tanks and may not match older, galvanized steel types. Kits are not the cheapest solution, but they are easy to fit.

Slip-over insulating jackets similar to hot water cylinder jackets are available for round tanks.

For either of the above options, be sure to measure the tank dimensions before you buy.

Polystyrene slabs used for loft insulation are easily cut to fit square-sided tanks. The slabs should be at least 25mm (1") thick. Fix with cocktail sticks and tape.

Left-over blanket roll or batts (minimum 75mm [3"] thick) can also be used, but they are less robust than slabs and trickier to fit. Secure the Pieces with string, and tape over any vertical joints. Cut another piece to fit on top of the lid and wrap them both in a bin liner.

Where the tank is without a lid, make one from an offcut of 12mm (1/2") chipboard or 9mm (1/3") plywood. Cut slots to clear pipes, then drill out the waste wood.

Other materials: Suitable adhesive tape, string or twine, cocktail sticks, funnel.

Tools checklist: sharp kitchen knife, tape measure, felt-tip pen.

1. Cut foam slabs to fit around the sides of the tank using a sharp kitchen knife. Cut slots to clear any pipes, but save the offcuts for taping back on.

insulating tanks

2. Fix the slabs together at the corners with cocktail sticks and reinforce with PVC tape. Then tape back the offcuts where slots were cut for pipes.

3. Cut a fifth slab for the lid and secure to the sides with tape.

Where there is an overhead vent pipe, drive a cheap plastic funnel through the slab.


Problem Solver

Awkward areas

There are likely to be places where space is too restricted to fit conventional insulation. In particular, watch out for outside taps and the holes where their supply pipes pass through walls. There may be a similar problem at the eaves, where overflows pass to the outside.

Pack these gaps with expanding foam filler, available in aerosol form. Although not cheap, it provides better weather protection than loose fill and is easier to handle.

problem solver - awkward areas

04. June 2011 by admin
Categories: Heating, Plumbing | Tags: , | Comments Off on Insulating Central Heating Pipes and Tanks


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