Cold Water Storage Tanks are very common in Domestic and Residential Sprinkler systems, mainly for category 2 and 3 systems, more often than not because the water board cannot guarantee the flow rate required for a sprinkler system.
When incorporating a cold water storage tank and pump set into a sprinkler system there are many options available:
Dedicated Sprinkler Storage Tank for full Sprinkler Demand
Dedicated Sprinkler Storage Tank utilising Infill rate to meet Sprinkler Demand
Combined Tank providing Peak Domestic Load and Peak Sprinkler Load
Combined Tank with serving Sprinklers and Domestic sized for Peak Sprinkler Load only with Priority Demand Valve on Domestic Supply
Options 4 and 5 with infill rate and tank undersized.
The purpose of the cold water storage tank, no matter what the configuration as per the above options, is to provide sufficient water supply at the flow rate required for the sprinklers based upon the duration required. However, once the system has been filled and tested how do we know that the tank always contains a sufficient amount of water as required for the sprinklers?
Lets look at what the British Standard BS9251:2014 recommends:
Section 5.8.4.1 of BS9251 under the Stored Water Supply states:
"An alarm to indicate low water levels should be provided for a stored water supply. The alarm should be situated in such a place or of sufficient decibels to ensure that the alarm can be noticed and acted upon."
The British Standard then offers the following in relation to Shared stored water supply under section 5.8.4.4:
"Where the sprinkler water is derived from the building’s stored water supply and the domestic pump set, the following recommendations should be met.
a) The water low level alarm should be set to operate at a point which is:
• well above the low level mark; and
• below the expected normal operational low water level, e.g. the range of top water levels the cistern is likely to experience throughout the day created by fluctuations in water supply (infill) and user demand (draw off). "
So the British Standard in its current form states that a low level alarm should be installed. Figure 1 of Section 5.8.4.2 provides the following diagram showing where the low level alarm needs to be situated on a dedicated sprinkler tank:
From the above diagram it is clear that the "Low Level" alarm in a Sprinkler Tank should be installed just below the required capacity of the system. This is different to a Low Level Alarm in a domestic water storage tank. When the term "Low Level Alarm" is used in a Domestic Cold Water storage tank supplying taps and toilets etc the low level alarm is situated at the bottom of the tank just above the suction pipe to the tank to prevent the pump from running dry. For protection of the Sprinkler Pump a "Low Level" Alarm may still be required just above the suction pipe you would have to refer to the pump manufacturers literature.
However for a combined tank at what level should the low level switch for sprinklers be installed. Our interpretation of the current standard is that it should be installed as follows:
Installing the sprinkler "Low Level" alarm as indicated in diagram 2 will allow an alarm to be raised when the peak domestic load compromises the effective capacity available for a sprinkler system.
The critical point in all of the above is that the Sprinkler "Low Level Alarm" is not the same as a Low level alarm in a domestic cold water storage tank used to protect the pump. The level at which the low level alarm should be installed at is to monitor the level of the effective capacity of the sprinkler stored water.
So now we have established what the function of the low level alarm is, what should it be connected to?
BS9251:2014 states that the alarm should be in a location where the alarm can be noticed or heard to allow remedial action to be taken.
A suitable option would be to connect the Sprinkler Low Level Alarm to a FloWatch 9251 Monitoring System. the FloWatch 9251 Monitoring system can monitor a low level switch with a normally open contact and will raise an audible and visual alarm in the event that water level drops below the required level. Not only will the FloWatch raise an audible and visual alarm, but the FloWatch Monitoring system comes fitted with an in-built GSM Sim Card which allows the unit to email out to a nominated email address in the event of an alarm, allowing remedial action to be undertaken.
Not only can the FloWatch monitoring system monitor tank level switches, it can also:
0 Monitor monitored isolation valves which will raise an alarm in the event that the isolation valve is not in the fully open position
0 Monitors booster set faults and will raise an alarm in the event of a fault with the pump
0 can monitor flow switches and will be raise an alarm in the event of a system activation.
Other Benefits of the FloWatch monitoring system include:
- 24 Hour battery back up
- Fully addressable
- Audible and Visual Alarms
- Can monitor upto 132 monitored isolation valves / flow switches from a single system
- Flow Alarm Output
- Fault Alarm output
- Easy Windows based setup wizard
Contact us today to purchase your FloWatch monitoring system info@flowatch.co.uk