Lagging a Cold Water Cistern


Never lay insulation under the cold-water cistern. Any warmth which comes from the room below will help to prevent the water from freezing. For extra protection. Jag the sides of the cistern and its lid. Make a lid if the cistern does not already have one, see how to make a cistern lid. Expanded polystyrene kits are available for lagging rectangular cisterns if you buyone. Make sure it will fit your cistern. Or you can use sheets of expanded polystyrene, which are available from most builders merchants. A cheaper alternative and the only method possible for round cisterns is to use glass-fibre or mineral-fibre blanket.


Things you will need
Tools Scissors; steel tape measure.
Materials Glass-fibre or mineral-fibre blanket, ball of string, plastic adhesive tape and large sheets of brown paper.

1. Measure the sides of the cistern and cut the blanket to fit so that it wiI be level with the top of the cistern. You will probably need about 1 widths.

2. Wrap the first piece of blanket round the cistern and tie it - not very tightly - with string at 9in (230mm) intervals.

3. Butt-join the second piece of blanket on top of the first, and make sure that there are no gaps between them. Tie the second piece in place with string also. Do not pull the string too tight and compress the blanket or it will not insulate effectively.
It you wrap a second layer of blanket on top of the first - so that the cistern is doubly protected - tie the string so that it is not above the string underneath.
4. For extra protection, cover the blanket with a large piece of brown paper. Hold the brown paper sheet- ing in place with plastic adhesive tape and string.
5. Lag the Fid with fibre blanket, overlapping the blanket already around the cistern.
6. To make the blanket secure, fix it in place with brown paper and adhesive tape.


This method is only suitable for square or rectanguar cisterns.

Things you will need
Tools Knife with a serrated blade (such as an old bread knife) for cutting sheets, trimming knife, steel tape measure and serrated spreader or old filling knife.
Materials Expanded polystyrene sheets Dreferablv 3m (75mm) thick and adhesive for expanded polystyrene (such as Evo-Stik ceiling tile adhesive or Unibond polystyrene adhesive).

1. Measure the sides of the cistern. Cut sheets of expanded polystyrene each about 1in (25mm) wider and higher than each side.
2. Cut holes in the sheeting to accommodate the pipes protruding from the cistern.
3. Place the sheets around the cistern to form a tight-fitting box.

4. Push a wooden skewer through the polystyrene at the corners to hold the sheets Jn place. You will probably need eight skewers in all. Put two into each corner, one at the top and one at the bottom.
5. Make a lid for the box with two sheets of expanded polystyrene. Cut one piece to cover the box exactly. Make the second slightly smaHer - less the thickness of the side pieces - so that it will fit inside the inner edges of the box. Stick both pieces together with adhesive for expanded polystyrene.

6. If there is a vent pipe hanging over the cistern, make a hole in the lid beow the outlet of the pipe. Place a plastic funner in the hole so that dripping water is directed straight into the cistern.