Water schematics – Microbiology issue 13…
Have you ever wondered why you’re always asked for site plans on an audit? We spend time drawing out the site layout and then drawing loads of arrows and lines on there, to depict the routes for waste, people, product, drains and water etc…
But why do we do it?
Most of us would probably admit that we never use these plans for anything, it’s just something that we get out once a year when we’re audited by our certification body.
So, what’s the point of them?
Well, they do actually all have a purpose, it’s just that we’ve missed the point of what they’re actually for. Probably, because when the auditor asks for them we get them off the shelf, blow off the dust, show them to the auditor and the auditor nods and carries on – as if to say, ” yes you’ve got them, we can tick that box”.
As you’ve probably guessed, if you’ve been reading Smart Knowledge for a while, I hate tick box exercises. If something doesn’t add value, I just don’t see the point on doing it. So, what is the point then? These plans are meant to be a working tool, to help in the identification of risks. I’m going to talk about the water plan (water schematic) in this post, as it’s a really useful tool that’s definitely under-utilised.
The purpose of the water schematic is to:
- To establish where the water comes into the site and therefore where the water infeed filter should be
- Identify and map out all the water pipe work leading off from this main infeed pipe, which allows us to:
- identify if there are any dead legs in the system
- identify the furthest points in the water system
- identify all the water output points
A dead leg is where a water pipe which once supplied water to a part of the factory, is capped off. For example, where a hand wash sink is removed, the water pipe is no longer needed and so, engineering come along and cap it off. This means that there is still water held in this pipe, which no longer goes anywhere – so it just sits there and stagnates. This stagnant water can then contaminate the mains water at the point at which the pipe connects to the main ring main.
I carried out some work recently at a site, where they had seen high TVC levels in their water. The have very kindly provided me with a copy of their water schematic to share with you, as a good example of how easy it is to unknowingly create a dead leg.
Here is their water schematic:
(click to open full view)
The site had recently removed a line from one of their units, in order to increase their storage capacity. During this process, they removed an unneeded sink from the area. The mains water comes in where the pink diamond is shown and the blue lines show the direction of travel around the site.
The sink was capped off at the point where the sink was, rather than removing the pipe back to the point where it meets the main ring main.
This means that the water in this pipe can’t go anywhere, so it sits there and stagnates. This then contaminates the water in the ring main, which is then picked up in the results of the water sampling micro.
Make sure that when old equipment is removed that requires water, that the water pipe work is removed and it is capped back at the ring main. If you have high results on your water micro, check your water schematic to make sure you’ve not got any historic dead legs.
Let’s use our example water schematic again to explain this.
The water in the ring main (the pipework that allows the water to go round and round) is constantly supplying other parts of the factory and it’s always on the move, so it’s unlikely that it’ll stagnate and become a micro problem.
Where the pipework routes away from ring main, we need to follow each route to see where it goes. The furthest part of the pipework away from the ring main, is where the water is most at risk.
Water output points…
The water output points at the end of these routes, must be on the water sampling plan. That way we are confirming that all the water on that route is potable (safe to drink). So, check your water schematic to make sure that all of your pipework furthest away from the ring main is being sampled, at the very least at the very end output point.
If you have any questions or can add your knowledge or experiences to this post, I’d love to hear from you. Please just add them in the comments section below.
We've tagged this article as: Utilities – water ice air and other gases
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