Category Archives: Services

Water, water everywhere

One of the great puzzles of Gwernybustach Farm was the source of the water. And the destination, but that’s for another day. We noticed lots of pipes all over the place, and some tanks further up the hill from the house, Water supply smallbut had no clear idea how it all worked.

Until Boxing Day, when it suddenly didn’t work any more.

We were expecting the failure mode of the supply to be frost related, as most of the pipes aren’t buried, but Boxing Day was fairly warm with no frosts. So, all plans for getting out the chainsaws and cutting down stuff were shelved, and on with the wellies.

We’d previously been told that the supply came from two sources. One from high up in the top field next to the road, and another from the side-stream, near to the ‘holy well’. But where was the problem, and what to do about it?

We started by working backwards from the house. Immmediately above the house are three tanks (F).The largest is about 1 cubic meter in size, and was totally empty. this looks to be the tank which feeds into the house. Above it are two smaller tanks, one of which has a connection into the big tank, and another which feeds it, so all three are cascaded together. The purpose of the smaller ones seem to be to act as settling tanks for the big one. All were empty

So off we went up to the top field, to find yet another small settling tank (G), entirely full of silt, but with no obvious outlet. George (Charlotte’s boyfriend) did some great work, up to his armpits in freezing water, and emptied-out all the silt, and uncovered an outlet pipe which wasn’t connected. So we connected it, walked back to the three tanks (F), and…..nothing.

So on to plan B. We’d previously noticed lots of tanks in the side stream, but hadn’t investigated any further. So off trooped George and I, in the gathering mid-winter gloom, to investigate.

At (D) there is a pipe with a tap on the end, and another which looks like it should connect to it. But no water coming out of the tap, so the problem must be upstream. we got as far as the tanks at (C) and (B) before it was just too dark to carry on. All were empty. Switched-on the tap, ready to go tomorrow…

So when Jackie and I came back on the 27th, we started at the inlet filter at (A). Blocked! This is where many happy, youthful hours spent padding and damming streams came in useful. A hour or so resiting the inlet filter (A) and and first filter box (B), and we suddenly had water flowing. Then just a matter of working downstream, connecting all the pipes and flusing out the silt, and finally, switching on the tap at (D) and connecting the extra pipe.

Result? Nothing at the house 😦 but some gurgling from a disused and empty pool at (E).

Finally, wondered as the tap at (D) was off when George and I first found it, I switched it back to off, and HEY PRESTO – we have water! Seems that there might be a ‘T’ junction somewhere between (C) and (D) which feeds the house, but with the tap (D) allowing the disused pond (E) to get filled. This pond might be a good header pond for mico-hydro ?

Anyway, we now have water, and we’ve decided to keep a constant flow through the system by leaving the water inlet to the pond running all the time. All we need now is a bathroom where we can use the water in comfort.


Starting the Hydro

We’ve decided to take the plunge and start the process of getting a micro hydro setup. The TGV Hydro site has lots of pictures of what the various bits & pieces look like.

The full report from TGV Hydro was a long and involved affair, but the highlights are:

  • Water head is 60m (see positions on the map), connected via 690m of piping to the turbine house
  • Peak flow is 35 litres/sec, for a peak power of 14.3kW, average 5.8 kW over the year. Bear in mind that this covers several months of the year where nothing is generated, as there not enough water. This is because although the stream flows all year around, there’s a legal minimum of flow which must keep going down the stream, and for some of the year, that leave nothing for the hydro. So suddenly wet summers become a Good Thing.
  • Total power estimated at 50,000 kWh per year, which is enough for 11 homes
  • We have decided to export direct to the grid, as there’s a handy eletricity pole nearby to the turbine house, and running a cable from there all the way to the house would be a significant additional cost

hydro catchment

The clever part is that they work all this out just by combining the siting of the intake with rainfall records.

Then assuming that the rain that falls flows into the stream, it’s possible calculate the water that flows past the intake.


All this produces this idea of the flow across the year.

flow profile

The Numbers

  • About £100k to build!! made up roughly of:
    • 10k to TGV to get are the design & permissions
    • 83k construction:
      • 30 for the turbine house & its kit,
      • 18 for the pipeline,
      • 8k for the intake,
      • 16k to connect to the grid,
      • …plus lots of fees and PM costs
  • About £12k per year income which comes from
    • Generation Tariff: 18.8p / kWh for the Feed-in-Tariff
    • Export Tariff: 4.8p / kWh for the power exported to the grid
    • The TGV report has all kinds of assumptions about how these might vary of the life of the system.
  • All this has loads of assuptions and options, but these are the headline items.

So, on this basis, a 100k investment for a potential 12k annual payback seems reasonable, assuming that these really are the costs, and the government doesn’t change its mind about loving green energy. As if they would…

Hydro Update

The first Hydro proposal suggested that we take as much as possible from the stream, and so generate the maximum amount of power.

But this meant that we’d have a large intake, a large pipe, a large turbine, and a large cable to connect the turbine to the grid. And they would all get used to their maximum for only a few weeks each year.

So TGV Hydro came back with plan B:

Plan A Plan B
Peak flow 35 l/sec 14 l/sec
Peak power 13.7 kW 7.2 kW
Average power over a year 5.8 kW 4 kW
Total cost £115k* £62k
Payback time 9 years 7 years

*Plan A needed lots more electrical infrastructure before it could be fed into the grid. Which we ended up buying anyway, as the combination of PV and Hydro needed a bigger transformer.

They key number here is the payback time, which is a proxy for return-on-investment – they key measurement for the viability of the scheme.

So, we decided on the smaller scheme, with the higher ROI.