If you laid out all the pipes in the Bristol Water network, they would reach from Bristol all the way to Madagscar!
Have you ever thought about all of the pipes that bring water to your taps? The water is cleaned at a Water Treatment Works, but how are the pipes themselves kept clean? We found out on a day out and about with the team who do just that.
Becks and Charlotte are Network Flushing Inspectors, working as part of a team of five covering the entire Bristol Water supply area and helping to maintain our almost 5000 miles of pipework.
They were kind enough to let us join them on a warm sunny day in Bristol, to explain about the process of flushing.
Starting with the basics, we asked Becks:
What flushing is and why it’s important to do it?
Over time, iron and mineral sediment can build up along the bottom of our pipes.
These sediments are harmless and do not cause any problems. However, if they’re disturbed, due to a burst main or when the emergency services use a hydrant, the sediments can get picked up into the water, temporarily causing a change of colour to your tap water.
Flushing is carried out to proactively reduce the risk of this happening.
Where do you flush?
A schedule of where and when to flush is created by the Network Modelling team. A lot of meticulous planning goes into creating schedules for flushing inspectors to follow each week, detailing which hydrants and washouts (valves) to open and in which order, for how long and the volume of water to use.
This means that only the minimum amount of water is used. Never unnecessarily wasting water, and ‘flushing’ only for as long as necessary.
How does the team actually flush a pipe?
So now we understand the schedule and where and when flushing is carried out but how does the team actually flush a pipe? Here’s what we saw.
Becks and Charlotte started by making sure the area was safe. Cones were set up around the area they were working in, and we were all donned in PPE. Safety first.
Becks used a lifting key and pry bar to open up the fire hydrant cover (you’ve probably seen these around, they’re often in pavements or verges, painted yellow, with a large ‘FH’ on them).
They removed the cap on the hydrant and connected a standpipe. On the end of this is a filter filled with dechlorination tablets.
This removes residual chlorine to non-detectable levels without affecting dissolved oxygen levels. Chlorine can affect aquatic life in larger quantities so removing it means the safety of wildlife can be ensured.
As the water starts to flow from the standpipe, Becks looked around to check where it was running to. Most of the time, water will naturally make its way to the nearest storm drain, but if the water is moving in the wrong direction, towards a building for example, then she redirects the water using a large hose.
The initial gush of water as the standpipe is opened, disturbs the sediment along the bottom of the pipe, and the water changes colour as it flows.
It starts off as a yellow/brown colour as the sediment is being cleared from the pipes.
Charlotte takes a sample of this water and tests it. She shows us the sample, as the water is left to settle in the pot, the sediment sinks to the bottom, just like it does along the bottom of pipes.
Testing is quick and simple, as the pot is placed into a handheld machine. The inspectors are checking the turbidity of the water.
Turbidity measures the levels of particles like sediment in water. As the turbidity of water increases, it becomes less clear due to a higher level of these particles.
Once the water turbidity reaches below level 3, then the flushing is complete.
Following the flushing programme created, Becks and Charlotte know how many litres of water need to flow through the pipe for it to be completed.
A digital display on top of the pipe shows how many litres of water have been used so far. This helps the flushing inspectors make sure they aren’t using more water than necessary.
When the number on the display, is nearing the number of litres indicated would be needed, they begin sampling the water again, and testing that it has reached below level 3 turbidity.
The water is looking sparkling clear now! And with the testing all complete. The hydrant is turned off, equipment is packed away, and Becks and Charlotte move on to their next location.
Does flushing affect your water pressure?
You may experience a temporary reduction in water pressure while flushing is carried out in your area. Occasionally you may experience a temporary loss of water supply but it will be restored as soon as the work is completed.
Does flushing affect the colour of your water?
If your water is cloudy or discoloured, this will only be for a short period of time, until the inspectors move to the next flushing location. Don’t worry, the discolouration is harmless. But it’s best to avoid using the dishwasher, washing machine or drinking straight from the tap until your water has cleared.
You can test to see if the pipes have cleared by letting your tap run for a few minutes.
How will we let you know about flushing in your area?
You will be sent a text message before flushing begins in your area, make sure your contact details are up to date so you receive the message.
Updates are also posted on Facebook.
You can sign up for notifications of any work in your area.
