Farmoor Facts
"If we turned on all the pumps we would reverse the flow of the Thames" (TW Site Ops Manager)
The TW Water Purification Process Simplified:
- The process starts with massive intake pumps that draw water from the Thames through metre-wide pipes into the reservoirs.
- From the reservoirs, it then heads into the ozone purification stage, which helps break down organic material and remove unwanted contaminants.
- Next, the water flows into the DAF plant—that's Dissolved Air Flotation, or as we like to call it, the bubble sludge maker—where microscopic bubbles lift sludge and solids to the surface for removal.
- Then it's on to RGF: the Rapid Gravity Filtration tanks, where water flows down through layers of sand and gravel to remove finer particles.
- After that, the water enters the GAC phase—Granular Activated Carbon filters (think of this as a giant industrial Brita filter)—to strip out remaining organic compounds, tastes, and odours.
- Finally, they add a touch of chlorine, as little as possible, just enough to keep the water safe as it travels through the network. Its then pumped up to Beacon Hill reservoir, ready to flow out of your showerhead crystal clear and safe.
Random Farmoor Facts:
- Farmoor 1 goes to the Farmoor treatment works
- Farmoor 2 goes to the Swinford treatment works
- It's 4.7 Km round both reservoirs on the track
- The usual draw off from the Thames is 70 - 90 Megalitres/day
- Turbidity testing ensures they draw clear water from the Thames
- Pipework etc is a mixture of Imperial and Metric due to it's age
- F1 & F2 are independent, but are interlinked
- With no abstraction from the Thames, F1 & F2 would give us 100 days of crystal clear drinking water
- The occasional Klaxon we hear is (hopefully) a test for toxic gas release
- The 5 Intake pumps can consume 145 Kw of power
- The same 5 pumps can abstract 300 megalitres a day from the thames
- No fluoride is injected into our water
The building of Farmoor Reservoirs
Farmoor from the air under construction and completed (above)
The Thames Water (TW) operated Farmoor reservoirs were completed in 1976 and now purify water drawn from the River Thames to supply Oxford and Swindon. If the Thames is low, TW can pump water back into the river so that it can be taken out at other facilities further downstream.
Farmoor tower and water outlet during the construction phase (above)
We sail on either the smaller Farmoor 1, capacity around 4.5bn litres, which was completed in 1967, or more often, we sail on the larger main reservoir, Farmoor 2, capacity around 9.25bn litres over 1sq.km at a depth of around 12m (40ft).
Sunset at Farmoor
Farmoor site features (above)
Downloads
Last updated 19:01 on 14 June 2025