What is the difference between a tap washer and a jumper valve?

A tap washer is a disc of material such as a polymer (plastic), or more rarely now of leather, which is fixed either to a loose spindle or directly to the tap spindle. See first three images opposite and the next Q/A for a description of a jumper valve.

What is a Jumper Valve & what is DynaValve?

A jumper valve is a safety valve and just another name for a tap washer on a loose spindle i.e. not just a simple disc of material. The valve is free to move up and down when the water is flowing so that besides acting as a normal washer shutting off the water when the tap spindle is screwed down it also acts as check valve if the street water mains are opened. When the mains are opened for service, water is drained out and this causes a partial vacuum in the plumbing system which can cause foreign substances and other contamination to be drawn back (reflux) into the mains. This can be very dangerous if the taps are connected to containers of weedicides or fertilisers etc. which could be forced back into a number of homes when the mains are turned back on. The purpose of a loose jumper valve is to prevent this from happening as well as enabling the tap or cock to be opened and shut.

Why do some overseas taps have fixed valves?

This is a matter for the local authorities and regulations but a fixed valve cannot provide the additional safety of the check valve function which a loose jumper valve provides. Loose jumper valves are by far the preferable type to use and often there is little difference in cost. The European Union is now looking into the question of check valve function with a view to making this compulsory. Fixed valves are not permitted on potable water supplies in Australia. Fixed valves cannot cause water hammer and this is probably the main reason they have been used in some other countries but there are better methods of controlling water hammer while retaining the benefits of a loose jumper valve. refer to the DynaValve features.

What is Water Hammer - this is Water Hammer, (best to download and play locally 1 MB mpg file.)?

Water hammer has a number of causes but the vast majority of water hammer is caused by the following;

1. the fast flowing water column coming to a sudden stop either when the tap is shut off or if the loose valve is unrestrained and the dimensional tolerances between the tap and the valve are excessive the valve can slam against the seat and bounce or oscillate (vibrate), (best to download and play locally 1.3 MB mpg file.) creating a wide range of loud noises. DynaValve will cure this and many other types of oscillations.

2. water is practically incompressible and when it is brought to a sudden stop it creates reverse pressure waves in the piping which either causes a loud bang if the water has no means of releasing this pressure wave gently, or it can dissipate the energy of the wave by vibrating the pipes if they are loose because they are not sufficiently anchored. Once a tap is shut off the water in the pipe is just as unyielding as the solid metal parts are with respect to the flexible washer or seal. Over-tightening will not achieve any better seal but it will simply cause the seal to spread radially and destroy the valve eventually.

3. water hammer is exaggerated by right angled bends in the piping because the pressure waves tend to bounce off them. In most plumbing it is not possible to avoid a number of right angled joints but where possible slow sweeping bends without joins are to be preferred.

4. water hammer is most often caused by loose unrestrained jumper valves being slammed against the tap seat and this is generally a result of the lack of a spring attached to the valve and or very loose tolerances between the valve stem (spigot) and the tap spindle bore. Typical situations which can cause unrestrained valves to slam against the tap seat are washing machine, dish washer and other horizontally mounted taps and cocks which are often connected to electric solenoids which shut off with great speed. Because the valves are unrestrained and often mounted horizontally they can rest some distance from the tap seat while the water is flowing and are then violently thrust back to the seat when the solenoid shuts the flow off. Valves fitted with a properly designed spring will return to the seat progressively and gently as the flow reduces thus avoiding the violent crash which occurs with unrestrained valves.

5. Loose tolerances are notorious for producing high pitched squealing sound as the unrestrained valve oscillates in the tap spindle bore because there is too much latitude to keep the valve moving accurately up and down as it is supposed to do. The valves are affected by a form of cavitation or vacuum which forms behind the valve stem in the tap spindle bore. This vacuum forms, dissipates and reforms creating a cycle in which the valve will jump up and down sometimes violently or vibrate at high frequency. If the tolerance between the valve stem and the bore are too great, which is a common problem, the unrestrained valve oscillates laterally as well as up an down setting up the high frequency squealing and thumping noises which can be so disturbing and can severely damage other components such as ceramic discs and seals in mixer taps in the same circuit. (Some mixer tap manufacturers will void your warranty if you have water hammer.) A spring loaded valve with the correctly designed stem and spring will control almost all lateral and vertical oscillations which cause water hammer. Spring loaded valves can also curb a lot of rattling loose pipes but they may not do this completely depending on the state of the pipes.

6. While water hammer will occur at low pressures, high pressures will increase the incidence and severity as the pressures rise. Most domestic and office plumbing needs only low pressures such as around 40 psi yet many mains supplies are delivered at pressures in excess of 200 psi. These pressures are dangerous and damaging to the plumbing but are the result of the need to deliver water over a wide area up and down hills etc. therefore it is not reasonable to expect the authorities to regulate the pressures suitable for individual buildings and pressure regulating devices should be fitted to the entry point of buildings where pressure regulation is required.

There is a misconception that because the water hammer pressure waves are high pressure waves that the spring needs to be extremely heavy to control the wave. This is incorrect as the actual volume displacement in the waves is extremely small and can be absorbed easily by a suitably design seal or valve such as DynaValve. Heavy spring tension continuously applied to the closed seal adds severe additional loading to the seal and usually results in a shortened service life of the valve among other effects. The Stainless Steel DynaValve spring is designed just strong enough to do the job required of it. This uses less raw resources and extends the life of the valve. Over 12 years and many thousands of valves no DynaValve spring has ever broken.

Sources of Water Hammer.

Cocks, taps and shut off devices of all sorts in plumbing systems with special reference to the following;

a) washing machine and dishwasher solenoids and cocks

b) water heaters, internally as well as externally placed cocks.

c) garden hose cocks.

d) water meter cocks and non return devices especially where more than one building may be attached to the same meter. Example: Gosford City Council NSW Australia, Java Doc. solved this severe problem using DynaValves and saved the ratepayers nearly $63 per service.

e) toilet water cistern cocks both standard 12 mm and 9 mm mini cistern cocks.

f) loose piping with insufficient clips and many right angled joints.

g) shut off devices external to the water meter i.e. nearby industrial plants.

High frequency "singing" noises are usually caused by high pressure leaks from worn, corroded or cracked tap seats. This cannot be cured by a jumper valve, the seat or the tap must be repaired or replaced. In-line Flow Control reducers of the static restricted orifice type can be a serious cause of very high frequency squealing noises. These were sold to reduce water flows where the mains deliver very high pressures and work simply by reducing the bore through which the water must pass through a reducing bore from typically 12 mm to about 1 mm or less.

These devices may be in use by neighbours and the noise may be transmitted through the mains to other places. This sort of noise can also be produced by 'tracking solar water heaters' which use mains pressure as the driving force. These systems use a small valve with a tiny hole to regulate the position of the collectors but these noises are usually of very short duration and low volume therefore they are often not noticed.

Curing Water Hammer. (best to download and play locally 3.2 MB mpg file.)

Because most water hammer is caused by loose jumper valves within buildings the first place to start is to attend to the indoor cocks. It is wise to have all cocks reseated. If you attend to your taps first, e.g. have the taps reseated and replace the old valves with DynaValves you have a better than 95% chance of curing the problem. Don't forget to remove any sharp edges left from the reseating. If that doesn't fix it then you need to look for the more exotic sources such as the hot water system, restriction devices or the water meter as noted above. Badly designed, fitting or dimensioned valves can perform a wide range of types oscillations to create an equally large range of sounds. Often it is the tap which is badly dimensioned and the valve should be spring loaded to compensate for this.

Valves and cocks attached to water meters and internal valves in water heaters must be serviced by a plumber. In some States re-seating must be done by a licensed plumber.

Some will claim that water hammer should be controlled by pressurised air shock absorbing cylinders, but this is only necessary in a small number of situations and generally where the source is not the taps or jumper valves themselves. Fitting a pressurised damping device such a compressed air cylinder is very much more expensive and to maintain than changing to an anti hammer valve such as DynaValve. Some will claim that jumper valves cannot cause or cure water hammer, buy and fit a DynaValve then judge for yourself, the difference is dramatic. Always check by installing DynaValves first, you could save yourself a lot of unnecessary expense. DynaValves do not make noises when they are working or if they do there is a serious wear, misalignment problem with the tap or the plumbing piping, not the valve. Refer to the "Features and Benefits of DynaValve" Java Doc..

Design of Jumper Valves.

DynaValve has been comprehensively designed from the physics through to the materials and although it appears deceptively simple the Valve has been subjected to a lot physical analysis, refer to the Detailed Features Illustration and How it Works. DynaValves are unique in the way they work. As noted above once the water is shut off it becomes as "hard" as the metal seat surrounding it therefore there is no point in applying undue pressure to the area of the seal over the water column, that only causes radial displacement damage to the seal.

The DynaValve does not apply significant pressure to the water column and the centre of the valve is able to act like a diaphragm helping to absorb the pressure waves of water hammer. These pressure waves involve a minuscule amount of displacement and with several of these valves in a circuit they act together to absorb shock waves. This is distinct from the anti hammer effects achieved with the specially designed spring. Run the DynaValve Slide Show, (best to download and play locally a Windows compiled .EXE file 2.6 MB) to see a more detailed explanation.

Maintaining your taps and cocks.

Never over tighten a tap. If the tap leaks after turning it off with modest torque (pressure) then there is a problem which needs investigation, if the cock is in good condition, most tap washers will shut of satisfactorily under normal torque . Most tap washer problems are actually tap problems i.e. corroded seats, cracked seats and bodies or misalignments created in the casting. Over tightening will destroy the valves and can also destroy some modern taps. If these taps are in inaccessible places this can be costly to fix. Most hand basin pillar cocks are so robust that they resist such damage but many cocks used as external taps and cocks commonly found in shower sets etc. are now cast with very thin walls and these are prone to distortion in manufacture and are extremely susceptible to over tightening. We have witnessed several cases of just this where the owner managed to crack the tap seat by applying massive torque to shut off the water which was actually leaking through the cracked seat. The tiles had to be removed to gain access and replace the fittings - expensive! The DynaValves survived however.

Lubrication.

Do not forget to clean and grease the tap spindle threads and "O" ring seal. Many tap greases are based on lanolin which is safe but it tends to absorb minerals and becomes stiff and less lubricating with time. Organic silicone greases are non toxic and safe.

DynaValve Grease is a water emulsion based silicone grease which provides heavy duty lubrication to the taps and cocks. It also designed to lubricate with a minimum film thickness.

Taps which are tight to turn off are generally in need of lubrication. Failure to keep the taps lubricated will result in valve failure because the operator cannot feel when the valve is being over tightened. This is a very common cause of valve failure.