THE PROVISION OF DRY RISING MAINS - FSSH 26

1.0. GENERAL

1.1. Dry rising mains should be installed in buildings where any floor is higher than 18m above ground level. Where there are floors higher than 60m above ground level, wet rising mains should be provided.

1.2. The number and disposition of rising mains should be such that:-

(i)One is provided for every 900m2 of floor area at each level other than ground floor;

(ii)Rising mains are not more than 60m apart in a horizontal direction;

(iii)No part of any floor area is more than 60m from a landing valve measure along a route suitable for hose lines.

2.0. DESIGN CONSIDERATION FOR DRY RISING MAINS

2.1. Pipework and fittings for dry risers should be of galvanised wrought steel. Pipework should be jointed by screwing and socketing.

2.2. Changes in direction should be made with standard bends. Elbows should not be used.

2.3. Rising mains should have a nominal bore of 100mm where only one outlet is provided on each floor level. If two outlets are provided on any level on any one riser the main should have a nominal bore of 150mm.

2.4. Each rising main should be provided with landing valves sited:-

(i)Within a ventilated lobby of a lobby approach stairway; or

(ii) In a stairway enclosure; or

(iii)In such other position as may be agreed with the Fire Authority.

2.5. Each riser should be provided with a 25mm drain valve at the lowest point of the pipework. The drain valve should be strapped and padlocked when not in use and its position should be clearly indicated with a notice reading 'Dry riser drain valve'.

2.6. If any part of the pipework falls below the inlet level, an additional drain valve should be provided at the lowest point of the pipework, together with fixed pipework or flexible tubing to conduct drained water to a suitable drain. A notice should be displayed reading 'Low Level Drain Valve in, (state location)'. The valve should be kept strapped and padlocked.

2.7. The aforementioned notice should be rectangular with white lettering on a red background in accordance with B.S. 5499 : Part 1. The letters should be lower case with the exception of the initial letters of the first word which should be upper case.

2.8. A suitable automatic air release valve should be fitted at the highest point in each rising main to allow the air in the pipe to discharge to atmosphere when water is pumped in at the base.

3.0. DRY RISER INLETS

3.1. A 100mm dry rising main should be fitted with a two way inlet breeching and a 150mm dry rising main should be fitted with a four way inlet breeching.

The breechings should comply with B.S. 5041 : Part 3.

3.2. All fittings should be accommodated in an inlet box complying with B.S. 5041 : Part 5. The box being positioned with its lower edge between 400mm and 600mm above ground level.

3.3. In selecting positions for inlets, due regard should be paid to the positions of underground hydrants, the possibility of damage resulting from falling glass and other possible occurrences during the course of a fire.

3.4. The position of the inlets should be clearly indicated in accordance with B.S. 5499 : Part 1 with minimum letter height of 50mm.

3.5. Inlet connections should be installed in an external or boundary wall of a building as close as possible to the position of the main which they serve.

4.0. DRY RISER OUTLETS

4.1. Outlets should be provided on each level of each riser. If more than one outlet is necessary on any one floor, additional risers in other staircases should be provided.

4.2. An outlet should be provided at roof level for test purposes.

4.3. Outlets should comply with the requirements of B.S. 5041 : Part 2.

4.4. Outlets should be installed with the lowest point about 750mm above floor level.

4.5. All fittings should be accommodated in an outlet box complying with B.S. 5041 : Part 4.

5.0. ELECTRICAL EARTHING

5.1. Dry rising mains should be electrically earthed. Those joints which do not provide electrical continuity should be bonded.

6.0. ACCESS FOR FIRE APPLIANCES

6.1. Buildings fitted with dry rising mains should have access roads for fire appliances to within 18m of the inlet connections, within sight of them and with unrestricted access thereto.

7.0. WATER SUPPLIES

7.1. It is desirable for two hydrants, or one double hydrant to be situated on one or two mains having an adequate flow of water for firefighting purposes. These hydrants should be not so close to the building that they may be inaccessible in case of fire, not so far as to entail loss of time in having to connect extra hose.

A distance of not less than 6m nor more than 15m from the riser inlet is considered satisfactory.

7.2. In all cases where towns main supply is involved, a water supply of 1500 litres/minute should be provided.

7.3. Consultation with the necessary water undertakers is desirable.

N.B. Additional information in respect of hydrants and rising mains can be found in B.S. 5306 : Part 1.
Source: NORTHUMBERLAND FIRE AND RESCUE SERVICE