Other Plumbing


By Matthew Marks

A water softener is a device which removes the chemicals in hard water areas which cause scaling: calcium and magnesium carbonate. It should not be confused with chemical/electrolytic/magnetic DESCALERS which merely attempt to prevent these chemicals depositing themselves inside pipes, tanks and shower heads. Nor should it be confused with a water FILTER, which removes bacteria, chlorine, pesticide residues etc. The chemicals which cause water hardness are actually removed by a water softener, but the resulting "softened" water is not the same as that in soft water areas, because it contains sodium compounds, as explained below.

Advantages of Softened Water

  • More pleasant to wash with: feels smoother; no soap scum; fewer skin problems (from wet shaving, for example)
  • No scaling of pipes, kettles, tanks, baths, showers etc.
  • Less washing powder, washing-up liquid, cleaning materials etc. required * Tea tastes better and concentrated soft drinks can be diluted more

Disadvantages of Softened Water

  • It is not recommended that softened water is consumed by those on a low sodium diet, and for this reason the cold tap in the kitchen is usually connected to the un-softened supply, or a third tap is fitted. There is a long-running debate about the pros and cons of drinking softened water, but sodium carbonate is not a dangerous substance. Softened water should not be used on pot plants either.
  • Some people do not like washing with soft/softened water because it is harder to rinse off soap.

Requirements of Water Softeners

Water softeners are fairly bulky, occupying most of a 60cm base unit if they are installed in the kitchen. Manufacturers seem to have put a good deal of effort into minimising the amount of room occupied, however, and there are many different formats. Access is required to add salt, and if a fault occurs (although I am not aware of any routine maintenance being required).

Most softeners require a (low current) electricity supply to operate valves and timers. Kinetico softeners operate entirely by water power.

Softeners require an overflow, with a free fall to the outside, and a drain, which can be a 15mm pipe and doesn't have to have a free fall as it is pressurised. The rising main needs to have a "pi" section of three valves (including a bypass) and a non-return valve to keep the water authorities happy. The softener itself is connected by flexible hoses, and these can restrict the flow rate if they are long.

Kinetico make a unit where the salt cabinet is separate from the rest of the softener. As the salt cabinet needs the overflow and access for filling, and the softener needs the drain and the rising main, this can ease installation in awkward situations.

Softeners do increase your water consumption by a significant degree: the figure for the Kinetico is that it uses 9 gallons for regeneration, after softening between 40 and 70 gallons: a 13-22% increase for a fairly efficient unit. This is in addition to the salt, which goes down the drain in one form or another. If you are worried on environmental grounds you should think carefully (bearing in mind that fewer cleaning materials will be used) if your water is metered you should think very carefully! If you can put up with scale in the toilet bowl, toilets can be plumbed to the un-softened supply. There is no point in feeding outside taps with softened water.

How It Works

Water softeners work on an "ion exchange" basis. The hard water is passed through a resin bed, where the calcium and magnesium ions are removed and replaced with sodium ions. The water will thus contain sodium carbonate. Periodically, the resin must be "regenerated" by flushing with brine. The salt dissolved in brine is sodium chloride, and during regeneration the sodium ions are removed and replaced with the magnesium and calcium ions from the resin bed. The waste water from this operation is flushed down the drain, as is that from "backwashing" which is performed to remove excess brine from the filter. The salt for regeneration is especially made for the purpose and is usually bought in 25kg bags which cost about 7UKP. How long the salt lasts depends on the hardness of the water and the efficiency of the water softener.

The Differences Between Water Softeners

The main differences between water softeners occur in how they go about the process of regeneration. This takes the order of 20 minutes, and during this time the resin bed is unable to be used for soft water. There are two main solutions, which are described below with their variants. To my knowledge there is no softener which actually senses when the resin is exhausted they all either meter the water (having previously been set to the expected level of hardness) or regenerate at a preset interval.

a) Timed Regeneration. The idea behind this is to regenerate while nobody wants to use water (normally in the middle of the night). If the softener only feeds a header tank then so much the better. The cheapest ones simply have an electromechanical timer which initiates regeneration at fixed intervals (Wickes being an example at 399UKP) others (e.g. Aqua Dial) have a microprocessor which estimates by metering the water over a period of days when the filter isn't going to last another day and initiate regeneration that night. Some (Aqua Dial included) also have a "proportional dosing" system whereby they only use as much salt as is calculated to be needed for the state of the filter. This should further improve efficiency.

b) Dual Resin Beds. Water usage is metered, and when one bed is exhausted, the other one is substituted and the first is regenerated. As this can happen at any time, the softener's efficiency is not dependent on the pattern of water usage.

There are also two types of salt: block and tablet. Some softeners can use both. Block salt is easer to handle and is claimed to be more efficient on machines which control the amount of brine to be used for regeneration by a change in level in the brine tank (which I presume does not include machines with proportional dosing). This is because the volume of water for a given change in level depends on how packed together and dissolved the salt tablets are, and is set to the worst-case scenario, therefore usually using an excessive amount of brine for each regeneration. Salt blocks, however, sit on a platform with only their bases in the water, so the volume of the brine tank does not vary.

Also, as previously mentioned, not all softeners require an electricity supply.


By Adrian Godwin 23/4/1996

Which? magazine has looked at these a couple of times over the last ten years or so - look them up in your local library for the full details. The conclusion they seem to have arrived at is that some units work for some people, other units work for no-one, but no units work for everyone. They haven't done particularly exhaustive research into why, and they recommend that you don't buy one without a money-back guarantee.


By Andrew Mawson 20/6/1996)

A trick I was told about by a tradesman for use when you cannot stop that last little drip of water in a pipe that needs soldering is to take some very fresh bread, form a tight ball from it, and force it into the pipe upstream of the drip using a long rod. When the joint is made and the water turned back on, the bread softens and can be flushed out through a tap.


By CliveE  7/5/1996

The other day I used one of those wine-saver thingies - a cam-operated bung - to temporarily stop-up a 22mm pipe. Actually this was the first time I ever found a use for it - I never leave half-empty bottles! It worked perfectly.


Matthew Marks 2/9/1998

There are three basic types of shower available.

1 Conventional Showers

A conventional shower is just a means of mixing hot and cold water, and spraying it at you. It is simple and cheap, but its performance is highly dependent on the water supplies to it.

If upstairs in a house with a conventional cistern-fed hot water supply, there will be very little pressure, and hence the shower may be very poor. By reducing the restriction of the shower head as much as possible, you may be able to get quite a lot of water pouring out from the large reservoir of the cistern, but with little force. This is an example of low pressure, but high flow rate. There may also be temperature fluctuations caused by water being drawn off elsewhere, and a thermostatic valve can be used to compensate for this.

If the hot water is at high pressure, such as from a combination boiler (q.v.) or multipoint or a Megaflo (q.v.), then the shower will be better, but may still be limited by the resistance of the incoming rising main. A thermostatic valve is recommended for combi boilers, because they sometimes produce rapid fluctuations in water temperature.

Conventional showers must be fed with hot and cold water of the same pressure, with the exception of a special valve which uses low pressure hot and high pressure cold. This also claims to boost the flow rate of the hot water by taking advantage of the pressure of the cold water.

2 Electric/Instantaneous Showers

These are available with built-in pumps for low pressure stored supplies, but normally they take high pressure cold water only, and heat it up instantaneously with an electric element. They are simple to install plumbing-wise, and allow you to take showers continuously, because they require no hot water supply. In the simpler devices, water temperature is controlled by a choice of two powers (plus no heat at all!), and by varying the flow rate. On the snazzier models there is electronic control of the heating element, giving variable output.

The main disadvantage with instantaneous electric showers is the power output. The largest I have seen is 10kW, which not only requires hefty cable from a separate fuse-way in the consumer unit, but is also less than half the power of even a low-end combination boiler: if you want a decent temperature, especially in the winter when the incoming water is colder, the flow rate will be quite low. They may also be quite expensive to run, as they are electrically operated and won't be on at cheap rate unless you shower in the small hours. However, this may be offset by not having to store hot water with consequent losses.

A characteristic of these showers is small but strong jets. This is an example of high pressure, but low flow rate. The shower head is designed in conjunction with the flow rate adjuster, and so the head supplied should be used.

3 Pumped/"Power" Showers

The second word is in quotes because it is misleading: one could argue that category (2) is a power shower as it uses electricity, and it is also being abused by the marketers because "power shower" seems to imply "excellent shower" in the minds of the public. What we are talking about here is a shower containing an electric pump, to boost the pressure, and therefore, if the supply is capable of it, the flow rate. Power showers are easier to wire than type (2) because they only need a low current supply for the motor, which consumes perhaps 500W or less.

Pumped showers MUST be fed from a cistern - i.e. you cannot use them with combination boilers, Megaflos, multi-points, etc. Quite apart from the fact that it is against water regulations to pump from the water main, you are unlikely to achieve much by trying to do this, because if its resistance. Pumped showers are usually only really needed when a cistern is employed anyway.

Pumped showers are less likely to suffer from temperature variations than conventional showers. They can produce copious amounts of water with a lot of force: high pressure, and high flow rate. They often come with shower heads that can produce varying spray patterns and mix air with the water. They can be extremely wasteful: it is drummed into one that a shower takes less water than a bath, and it is possible to be blissfully unaware that this may no longer be the case with such a beast!

The simplest pumped shower is a device which you screw to the wall and connect between your existing mixer and shower head with flexible hoses. It has an on/off switch, and the shower will still function with it switched off, as the pump chamber does not present much resistance.

More sophisticated models include a mixer within the case, and are plumbed permanently into low pressure hot and cold supplies. They usually have a combined on-off switch and mechanical flow rate control, and may vary the speed of the motor.

More sophisticated still are the separate pumps. The cheap ones connect to the mixed water the expensive ones have two chambers which connect to the hot and cold supplies. They may be used with manual or thermostatic valves.

Cavitation and air in pumped showers

The nearer the pump is to the supplies, the better it will operate (and obviously a two-chamber pump can be put nearer to the supply). This is because a pump may be capable of producing a very high pressure, but can only "suck" at one atmosphere before a vacuum is created and performance will not increase. Even before this, "cavitation" (tiny vacuum or dissolved air bubbles) will start at the impeller blades, and this is very bad for the pump. Water from the rising main contains dissolved air, and heating it up encourages it to liberate this. It is therefore a good idea to connect a shower pump to a hot water cylinder with a "Surrey flange" or an "Essex flange", which has a short dip-tube to avoid trapping the liberated air rolling up the sides of the cylinder. (A Surrey flange fits into the top of the cylinder and has an additional output for the existing connections an Essex flange is a dip-tube only and goes into a new hole made in the cylinder.) Surrey/Essex flanges will also help to avoid interaction between the pump and other hot water consumers.

A shower pump should not be installed at a high point in the system: trapped air will be difficult to expel, and, in a worst case, the pump may not operate at all as it is not self-priming: i.e. it cannot pump air.

Switching of separate pumps

Separate pumps have automatic switches to operate them. Positive head pumps are used where there is still some flow when the pump is off, i.e. when the bottom of the cistern (this is used as the datum, as it is a worst case) is significantly above the level of the shower head. The flow switch(es) activate the pump as soon as the valve is opened and water starts to flow, and deactivates it as soon as the valve is closed and flow ceases. Another reason to keep air out of a shower pump is that it might cause these switches to oscillate, in the following manner: 

1) a sudden increase in pressure (such as water hammer from a valve being closed quickly) pushes water through the pump as it compresses an air bubble in the system

2) the water flow switches on the pump, causing more water to flow as the bubble is compressed further

3) the air pressure reaches the pump pressure, the water stops, and the pump switches off

4) the air bubble pushes the water back again

5) the momentum of the water causes the air to expand beyond equilibrium

6) the water eventually stops, and then flows back again, as the air pressure is lower than it, and the cycle starts again.

Negative head pumps allow a shower head to be higher than the bottom of the supply cistern, and are useful in flats and for bathrooms in loft conversions. These require pressure vessels, non-return valves and pressure switches, and are therefore rather more expensive than positive head pumps. The pressure vessels are on the outlets of the pump, and are monitored by the pressure switches. They contain an air chamber and a diaphragm, rather like for a sealed heating system (q.v.), and allow a significant amount of water, which is essentially incompressible, to flow in or out for a given change in pressure.

The pressure switches are normally closed, causing the pump to charge the pressure vessels. This will open the switches, the pump will stop, and the non-return valves will ensure that the vessels remain charged. There will now be enough pressure in the system to allow water to flow out of the shower, and as soon as this happens, the pump will operate. Leaking shower valves will be obvious by the annoying intermittent operation of the pump that they cause!

Other considerations with pumped showers

Pumped showers can be noisy. There is not much that can be done about this in the case of the ones mounted in the showering area, but separate pumps should be supplied with flexible couplings to reduce the amount of vibration being transmitted around the house through the pipework, and they can be supported on rubber mats to reduce noise transmission through the house structure.

Pumped showers may require more sophisticated measures to avoid water escaping from the showering area: some screens, etc., are not recommended for use with them.

Some shower pumps operate from Safety Extra Low Voltage (SELV), e.g. 24V, and are supplied with separate transformers which are installed well away from the water. This, in theory, reduces the risk of an electric shock from them. My opinion is that approved mains pumps will have been rigorously designed and tested to be very safe, and ***if installed properly*** will be as safe as SELV pumps. Naturally, pumped and instantaneous electric showers should be connected via an RCD (q.v.), and should only be installed by those who are confident in their abilities to produce safe electrical installations.


By Tim Downie 29/1/1997, added to by Matthew Marks 22/10/1998

Given time, all washing machines leak. If the leak appears on the floor, creeping out from under the front of the machine, the likelihood is that it is the door seal that needs replacing. If the puddle seems to be emerging from the back of the machine, it's probably the pump. Pump leaks tend to be small and you only usually find them when you happen to pull the washing machine out of its cosy hole under the worktop.

Door Seals

Have a good look all around the inside of the door seal. The hole can be quite unobtrusive and need not be at the bottom of the seal. If you find a hole then pop along to your friendly neighbourhood washing machine parts supplier with your full washing machine name and model number and get a replacement.

Pull your washing machine out of the dusty hole where it usually resides and unplug it. Open the door and pull the edge of the door seal off the lip round the door on the front of the cabinet. Fingernails usually suffice for this. Having done this, insert your fingers through the gap outside the door seal and have a feel around the edge of the drum where the inner edge of the door seal is attached. If your machine is anything like mine then you will feel a slim metal "jubilee clip" type retaining wire holding the door seal tightly to the drum. Remove the top of your washing machine. This will expose lots of wires and switches all at mains voltages. If you haven't already done so, make sure that your machine really is unplugged. Look down the front and see if you can spot the clip holding the door seal. It's usually quite a long way down and relatively inaccessible so a long screwdriver or 1/4 inch drive socket set with extension is required. Slacken the screw/bolt and then simply pull the door seal off the drum.

The new door seal will look like a floppy tube with no apparent correct orientation. Look carefully around the rim that attaches to the drum and you may find an edge with holes in it. This point should be lowermost, as it is there to allow water in the bottom of the door seal to drain back into the drum. If you fit it the wrong way up, your new door seal will fail prematurely.

Now comes the tricky part. Take the retaining clip and fit it loosely to the inner door seal lip. Make sure that the retaining clip screw is orientated in such a direction that you will be able to tighten it from above. Wiggle the door seal onto the lip on the drum, making sure that the holes (if any), are at the bottom. When you think you've got it on fully, go to the top of the machine and tighten the clip. Now you can stretch the outer lip of the door seal over the lip around the door on the cabinet, making sure that there is no axial twist in the seal making it wrinkled. Wrinkled seals die young. If you can't seem to get rid of a wrinkle then this means that there is a slight misalignment twixt drum and door. A common cause of this is breakage or detachment of one of the springs that hold the drum centred. They can be a bugger to reattach but it's worth doing as misalignment is another cause of early door seal death.

Put the top back on and congratulate yourself on a job well done.

If anyone has come across a door seal fitting that differs enormously from this plan, feel free to amend it.

Pump Leaks

The pump on your washing machine is an uncomplaining little thing, and rarely gives rise to serious problems. With age however, the seal around the motor shaft can start to leak and the only remedy (as far as I'm aware) is pump replacement.

Unplug you machine, whip the back off and have a good look with a torch if necessary to see if there are tell tale signs of water leaking past the pump shaft seal. (If you're not familiar with these things, the pump is the small motor near the bottom of the machine with a small fan attached to one end of it and a pump chamber with two hoses attached to the other.) If it is leaking, take your washing machine name and model number around your local parts supplier. There's a good chance that they'll have to order it so you might prefer to do this bit by phone.

When you get your pump, don't be too surprised if it doesn't look the same as the old one. Many of the metal components will probably have been replaced with plastic ones, but as long as the mounting screw holes and hose positions are the same, don't worry about it. Removal of the old pump and replacement with the new is usually very straightforward.

Machine won't spin, empty, or overflows

A very common cause of these problems is blockage of the line to the water level switch. Near the bottom of the drum is a connection to a small tube which rises to well above water level, where it is connected to the switch. As the water level rises, the pressure of the air in the tube increases, and compresses a diaphragm inside the pressure switch, causing two or three sets of contacts to change over at different water levels. It is very common, especially in hard water areas and when the hottest wash is not used, for limescale-based gunge to block this tube and prevent the air pressure switch from operating at all, or operating quickly enough. This may make the machine think that it is empty when it is full (and will thus overfill), or full when it is empty (and will thus refuse to spin).

On Hoover and possibly other machines, the connection to the drum is via a small plastic bottle, which often gets full of gunge. It seems to me that this bottle is either to damp the pressure switch (preventing it changing over as the washing sloshes about) or to allow more gunge to collect before it is rendered inoperative.

Pressure switches are easy to test: they are sensitive enough to operate by blowing into them, whereupon you should clearly hear the click of the contacts. With all the wires disconnected, an ohm meter can be used to check the electrical integrity of the switches - a bit of experimentation should establish which contact is which of the changeover mechanisms.

Pipe Bending

These documents give instructions on how to mark out accurate bends and offsets using either a bending machine or springs: