Posted By John Webster
K Babu Rao,
Probably your best source of technical information will be the supplier of the emergency shower and eyewash units. However, I will try to answer as best I can.
You say that the water supply is a potable water supply - as it should be. However, you request information on water storage. I must therefore assume that your drinking water supply comes from storage tanks and not directly from the municipal water main. If running from a reliable mains supply, then storage should not be required provided that it is possible to suspend the hazardous activity in the event of loss of supply.
To meet ANSI standards, the water pressure at the shower head, under running conditions, should be 2.1 barg (30psig).
Water supply must be capable of delivering the rated flow (see supplier) to the shower/eyewash for a period of at least 15 minutes - so your minimum additional storage will be that required to supply the largest rated shower unit for that period. If there is the possibility that several people could be involved in the same incident (unlikely in a lab, but risk assessment is required) you may have to allow for more than one unit being used simultaneously.
Your initial water temperature is probably OK, (ie >15 degrees C) but you should take account of the effect of any prolonged use drawing cooler water (underground main?) from the supply, so if you are not sure, check the temperature where the water comes into your premises.
Normally galvanised iron pipe should be OK, provided that your water has pH > 7.5 or thereabouts. PVC is ok, and fire is not a real problem. If the fire is severe enough to soften the pipework to the point of bursting, then the release of water will be welcome! However, pvc does tend to support the growth of biofilm more than other plastics and is not generally used in drinking water applications. LDPE (alkathene) is commonly used, though appropriate potable water grades of HDPE would be OK as well.
Most important is to design the system so that there is regular flushing of the pipework e.g. at the end of the line there is a tap which is in regular use and which can be opened to full bore periodically to flush sediment from the pipes. There should be no "dead legs", and branches to other taps and especially to the showers/eyewashes must be as short as possible. If pumped, consider a return from the furthest point to the storage tank.
Test and flush each unit weekly, and keep a record.
Finally, maintain the system as you would any stored drinking water system, with regular tank cleaning, install filters if your water is turbid, and check the effectiveness of disinfection (eg chlorine residuals if thats how your water is disinfected). Tank lids should be sealed, with filters on overflows and vents etc. Remember there may be a risk of Legionella developing in poorly maintained systems at your ambient temperatures.
Hope this is of help
John