What’s wrong with water softeners?

Cambridge has hard water and it scales up our appliances. Some of them we can clean with a bit of effort, but some are not so easy. You can clean the heating element in your kettle just by soaking in hot dilute vinegar – but getting at the heat exchanger in your hot water cylinder is a tricky job. The obvious answer is a water softener. 

There are two problems.

1. Water softeners use extra water and we are already water stressed in this area.
2. Water softeners use a lot of salt and this is bad for the environment. It has to go somewhere: usually it ends up in our rivers.

How bad is this and what can we do about it?

Rainwater harvesting: dammed by regulation

For the whole of the East of England water supply is an increasing problem. Here in Cambridge we need to reduce the amount we take from our aquifers by about half in order to protect the chalk streams. This will be achieved with a combination of reducing leakage, reducing demand and increasing supply (by building large reservoirs). One way to reduce demand is to harvest rainwater for use where it does not have to be drinking quality, such as flushing toilets. 

Eddington in North West Cambridge has a rainwater harvesting system for 3000 homes, the largest in the country. It is often cited as an exemplar for water saving, with every home having two supplies: one from rainwater (non-potable) for use in the garden, in the washing machine and flushing the loo alongside the one from the mains for everything else. As I recall, the pipework has different colours. The rainwater is stored in a rather beautiful lake and is fairly clean but not as clean as the water we get from the chalk aquifer; there is equipment for basic treatment on site. The problem is, the rainwater harvesting supply has never been commissioned due to concerns from the Drinking Water Inspectorate (DWI). 

 

Brook Leys Lake at Eddington – stores rainwater for supply to homes, but not commissioned for use.

Smart meter for detecting water leaks

Many of us now have smart meters for electricity and gas, but we are starting to see smart meters for water too. They may help you with reducing water use – which is very important because of climate warming as well as the growing population. However, one of the key benefits is going to be detecting leaks – for water companies and for consumers. We had a water leak a few years ago and we would have spotted it a lot quicker if we had a smart meter!

We take water for granted and don't think about it. Smart water meters will help us track our use and detect leaks.

What is a smart water meter?

Smart water meters usually have similar features to smart energy meters so they record how much you use, often hour by hour, and send the readings to your water supplier (or their agent). This means there is no need for a man to come and read the meter in person and you can get much more frequent updates as to how much you are using. Southern Water is trialling a clip-on device that fetches readings from the old meter and sends them wirelessly to a datacentre [1]. In Coventry and Warwickshire, Severn Trent is testing new meters that allow you to check your consumption hourly if you want [2]. Anglian Water is rolling out something similar for all customers [3] and so is Thames Water [4]. They aim to have most customers on the system by 2030. 

Would water trading between regions reduce future costs?

Water supplies are under pressure again due to the very dry weather. So here are some facts about water usage: how much we use at home compared to businesses and industry, how this is expected to change, and how the cost of trading water between regions compares with new supply.

Insights from studies of water shortages

Water shortages are increasingly common as an impact of climate change. Rainfall is not predictable, but most places have sufficient water reservoirs that shortages happen slowly and can be foreseen. At some point consumers are asked to be careful, and as disaster looms nearer these messages become increasingly frantic. Does this remind you of anything else? Climate change also happens slowly and not exactly predictably and exhortations to reduce emissions are becoming increasingly frantic.  Whether or not we will avert disaster remains to be seen. In this post I discuss insights from three journal article relating to damage limitation in drought. The first is about the near disaster in Cape Town during 2017/2018, from the view of the Cape Town water supply management. The second is also about Cape Town but from the view of residents – how the shortage affected different kinds of people. The third discusses how residents of Fortaleza (in Brazil) responded to increasing water prices during a drought. 

Options for water supply in Cambridge.

CambridgeshireLive news recently reported that plans for new homes in Cambridge could be stymied by lack of water supply. I have been reading the report behind these findings [1]. It is good to know that the water supply constraints are being taken seriously at last  – and that solutions are on the table too. Demand side measures include leakage reduction, rainwater harvesting in new developments, and prioritising public water supply over agricultural use. Measures to increase supply include land management schemes to improve water retention and possibly hooking up to a new reservoir in Lincolnshire.

Hair washing - survey results

Thanks to everyone who completed my survey on how we wash our hair in the shower. I am concerned about this because of my general concern about water use as well as energy because showers can use a lot of both. Your shower could account for half your water consumption or even more*. This is more of an issue for people with long hair, although you do not have to have long hair to take a long time in the shower. The results of the survey demonstrate a wide range of behaviour, even though I am sure there was a tendency for respondents to be more eco-conscious than average - otherwise why would they take the time to fill in my survey? Anyway, here are my main findings.

How much water do we use washing our hair?

A friend told me yesterday her lodger spends 20 minutes in the shower each day - but she has long hair. (We were discussing the pros and cons of solar hot water panels). Since I have short hair I am very quick in the shower which I like because it means I have more time for other things. In addition, less time in the shower means less use of water and energy to heat it. Both water and energy are valuable and water can be scarce at times. If you already have efficient toilets it is quite likely that your biggest water consumption is the shower. Try my water calculator to check. So how much water and energy do we use washing our hair? How does this compare to our overall consumption?

Please fill in my survey
It is difficult to find good data on hygiene habits so I have compiled a short anonymous survey. If you wash your hair in the shower please fill this in. In the meantime, here are some estimates and suggestions for how we can be more efficient with washing our hair.

Water saving again

Siphoning the bath water into the water butt.

Rainfall has been very low for the last few months across the country but especially so in the East of England. Our water butt ran very low a couple of weeks ago and we have resumed emptying bath water into it. We now have a shorter hose and attachments which makes this much easier!

Here in Cambridge we get our water from an aquifer which protects us from short term droughts, but last year the level dropped to record lows and there were serious problems with low flow in important chalk stream habitats. The level did recover this last winter, but I fear a repeat this summer, if we are not careful with water. Please do what you can. Here is some more background on the issue and some water saving tips.

How is a thermal store different from a hot water tank?

People often ask if they can use heat from their solar panels for heating as well as hot water. The short answer is no, because the solar panels heat your hot water tank which supplies hot water to your taps, not your radiators. The long answer is you could, if you installed a thermal store instead of a hot water tank, though this may or may not be a good idea. A thermal store is also a big tank of water it works in a different way so it can be used for space heating as well as hot water. Thermal stores can be useful in various situations:

• You can combine heat from different sources, e.g. solar panels or a wood stove as well as your boiler
• You can store heat to optimise use of your heating system - for example if it is inefficient to turn on and off according to demand (particularly useful for log burners but also for other biomass boilers or even heat pumps).
• It can store heat when power is cheap for use when it is expensive. For example, using a thermal store you can avoid running your heat pump at peak times and get a cheaper tariff (at least you will when we all have smart meters and time of use tariffs are available).

The size you need depends on what you want to do with it.

How much less water do modern houses use

Cambridge is growing and more people means more water consumption, which is a concern in this area. Will the new homes use as much water as existing ones? Building regulations require that new homes are fitted with water efficient appliances so that an 'average' person will use no more than 125 litres/person/day (lpd). This is considerably less than the UK average 141 lpd. So what is an 'average' person? Using the water calculator specified in building regulations I have estimated water consumption for this mythical individual using water efficient appliances versus a traditional context - by which I mean one from a few decades ago. Based on this estimate, even if all new homes use the most efficient appliances that would not be enough to keep Cambridge's usage within the allowed limits.

Here are the headline figures: the efficient house comes in at 104 lpd compared to 146 for the traditional house, and 47% of the difference is due to savings from flushing the WC. This chart compares the two.

Total use Efficient home 104 lpd, Traditional 146 lpd. For assumptions and use factors see below.

You might like to compare your usage with the 'average' person. If you use more then you could probably save more too.

How much water do power stations use?

It is world water week and the power generation sector is often blamed for high water consumption - how high is it really? First the headline figures. Current water consumption by UK power stations comes to around 13 l/person/day [1][2]. That is less than a tenth of the amount we use at home [3].

However, the amount of water used depends on the technology. Wind and solar power generation need no water at all but most nuclear and conventional power stations use water for cooling. Coal power stations use more water than gas, partly because they use water for cleaning sulphur out of the flue gases as well as for cooling. Nuclear power plants also use more cooling water than gas. This is partly because they are less efficient so they have to dump more heat and also because they don't generate any hot flue gases, so all their heat has to be dumped through the water cooling system.

How much water is it OK to waste?

All water companies waste water through not fixing leaking pipes. This is OK up to a point. There is something called a 'sustainable economic level of leakage' which is the level where the cost of fixing leaks and the cost of not fixing them balances out, taking into account environmental costs. Obviously environmental costs are hard to put a finger on. So what is acceptable?

Think energy savings - think water savings too.

I have long been concerned about energy and climate change but recently I have been thinking about water too. There are a lot of similarities - in supply limitations, environmental impacts, and the fact that they are essentials for life but (for us in the developed world) extraordinarily cheap. The principles for water saving are the same as for energy too. If you have concerns about energy and climate change you should be thinking about water too.

My flood story - why we need smart water meters too

I am somewhat obsessive about energy use and read our meters weekly, as I have said before. But I am not so diligent regarding water use. If I was, I could have saved us £100s on our water bill due to a massive leak we did not notice!

Our water bills should say:
Your consumption:

This period: 230 litres/day
Last period: 200 litres/day

Your consumption has increased 15%

You can switch energy suppliers - why not water suppliers?

Currently we can choose and switch between energy suppliers but not water companies. Until now water companies have been allowed to enjoy a natural monopoly in each area, with regulation from OFWAT to ensure that prices are fair and services are good. However, as from April next year business customers will be able to switch supplier and OFWAT has produced an evaluation of costs and benefits from extending this to residential customers. They report a number of potential benefits [1]. But given our experience of energy suppliers, do we really expect competition between water companies to realise those benefits?

How much electricty does the solar hot water panel pump use?

We have solar panels for heating our hot water. As well as using free energy from the sun, they use some electricity - this powers the pump that circulates heated water through the hot water tank. I have been assured that this pump does not use much electricity - finally I have been able to confirm this by measurement (more or less). In July, I estimate electricity for the pump is about 3.6% of the heat obtained. In winter the pump energy goes up to 6.4%. The reason the yield is not so good in winter is that the water from the panel is not so hot. The pump works just as hard but there is less heat being delivered. However even then, and allowing for the fact that the pump uses electricity whereas our backup water heating is from a gas boiler, we still get 80% savings on carbon emissions.

This is only a sample of one and your system may be different. Also, there are some uncertainties around my measurements. However, I believe these figures are at least plausible. Keep reading to find out how I made my calculations.

How much does your bath or shower cost?

When we have a bath or a shower we don't just pay for heating the water, we have to pay for the water too (if we have a metered supply). Taking both into consideration, I was surprised to find that the water costs more than heating it! In fact, assuming you heat by gas with a reasonably efficient system, only about 40% of the cost of your shower or bath is for the heating. In Cambridge, the total cost of an average bath is about 36p and a shower probably 9-22p - depending on the amount of time you spend in the shower and the flow rate. These figures are shown in the chart.

Cost of bath/shower etc. in Cambridge. The assumptions are discussed below.

Solar hot water for combi boilers

Making use of solar hot water with a combi boiler is difficult because most combi boilers don't work with preheated water. However, Viridian Solar have a solution for this called the Solar Pod. It relies on the fact that most combi boilers will work with tepid (not hot) water up to about 30C: about 1/3 to 1/2 of the way to the temperature you are aiming for (assuming you want 45C-55C).

What is normal energy use?

Households vary enormously as to how much energy they use and what it is for. This is the clearest lesson I have learned from my analysis of the Household Electricity Survey(HES) [1] and I see it in data sets for other sorts of energy too. I recently read a report about a 'Smart Community' project which aimed to reduce energy use in households recruited in Kingston upon Thames[2]. One of their findings was that when people discuss their energy use habits this seems to reinforce their current usage rather than promote savings. However, when I got to think about it this was not so surprising, and I suspect it leads to increasing energy use rather than savings, at least in some categories.