Reasons for low water pressure

Low water pressure at tap

Low water pressure usually goes unnoticed

One of the most common reasons for low water pressure occurs temporarily during busy periods, for example between 7.00am- 9.00am.  Peak periods of water usage will have an impact on the water pressure, in most instances, the fluctuation will go unnoticed unless the water pressure drops below the minimum pressure required to operate a boiler or shower. An example on this would be if you were run a tap and then flush the toilet in your bathroom, while the toilet is going through its refilling cycle a noticeable drop can be observed at the tap. Peak periods of the day when the water demand is high there are thousands of people using large amounts of water and all at the same time. Pre-Installation Checks will give an installer a good idea of what type of shower or boiler is most compatible with the water demands in your area.

hot water gravity system

Low of water pressure on gravity heating systems

On some of the older types heating systems, the hot water is supplied via a gravity system where as the cold water is fed directly from the mains.  A noticeable difference between the hot and the cold supply is evident on these types of systems.  Gravity systems hot water supply can easily be restrained by merely placing your thumb over the hot tap. The hot supply is delivered via a cylinder accompanied by a cistern in the loft,  the weight of the water contained in the cistern adds the pressure to the water supplied at the hot taps.

Quite often the reason for low water pressure is an air lock within the system; air is trapped this restricts the movement of water.  The cold supply which is delivered at mains pressure is never affected by air locks.  Air locks usually occur after draining the system down, at this point the hot water supply is susceptible to air being trapped.

Strategically placed air vents can help to release trapped air if a system as a problematic history of repeatedly encountering this problem.   Air locks can also be forcibly removed by an experienced plumber that is accustomed to working on these types of heating systems.

High-rise blocks constructed during the 1950s – 6os will have significantly less water pressure than what will be found in most homes.  An apartment at ground level will not be affected as mush as one on the top floor.  The requirements for water pressure at the time would have been targetted towards delivering an adequate bath and a constant supply of portable water.  Installations such as electric showers and combination boilers didn’t exist at the time.  With these types of appliances, pressure is crucial to achieving a successful operation.   Adaptation can be made to an existing water supply impaired by low pressure, the installation of a pump can help boost the water pressure to meet manufactures requirements.


Low water pressure in rised high blocks rised blocks

Other reasons for low water pressure

The lack of water pressure can also be the result of the excessive use of elbows, every time a  90-degree angle is fitted the water pressure as to overcome a slight restriction, and still be able to deliver an acceptable amount of force at the water outlet.   Under normal circumstances, a drop in pressure would go unnoticed.  However, a pressure drop like this could be detrimental to a system that is already low in pressure.

The navigation of water can be achieved with a minimal pressure loss by opting for the shortest route possible. Using manually constructed copper bends instead of elbows, plastic pipe is flexible if strategically placed it can navigation the water supply without the added restriction of numerous bends.

The standard type isolation valve as a narrow bore,  this is every restrictive and should be avoided if pressure related issues are evident.  However, there is an alternative to this device, a full bore isolation valve this will isolate the water supply with minimal restriction to the flow.


Water flow restriction

Damage to underground pipework can also affect the water pressure.  The reason for the drop in water pressure is the damage to the supply pipe creates an interruption to the transportation of the water supply.  The momentum of the water supply will be affected while the pipework is damaged.  Noticeable signs of an underground leak would be the motion of the meter dial when all water outlets have been shut off.  The sound of a constant running water, or unexplained damp patches in areas that were previously dry.


Fault find a pressure loss

If recent work as been carried out and there is a noticeable difference to your water supply, it may be a good idea to check that the stopcock is fully open.  Narrowing for the water channel within the stopcock may be affecting your water supply.  Isolations valves can also have this effect, if not fully opened.  The effects of this will be apparent at the designated points where these valves are fitted,  i.e., beneath basin taps, kitchen sink,  and also the water supply to the toilet.

A pressure loss can often be localized to a particular water outlet, i.e.,  a tap that was previously flowing at an acceptable rate,  but as now become a dribble.  What could be the problem?   If all other outlets have adequate pressure but the problem seems to be coming from a single tap,  blockage of the pipe is very unlikely,  a restriction of flow through the tap would be the most obvious choice.  If in doubt always consult a qualified plumber.








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