TECHNICAL 39
How do I do fault finding on
my PCV without removing it from the system ?
By Patrick Gordon of Calafrica ( technical @ calafrica . co . za )
Often the Pressure Control Valve is replaced unnecessarily . Manufacturers often get the complaint that the valve worked for many years and then started leaking , however the new valve started to leak within days of being fitted . So why are the new valves not as reliable as the old ones ?
Simply put they are just as reliable . In most cases the old valve should not have been removed as it was not faulty . When the valve starts to leak and it is old , we automatically , and incorrectly , assume that the valve has come to the end of its life . By doing some simple tests we can ascertain what the cause of the leak is .
Before doing anything with tools we need to eliminate normal expansion as the cause . The expansion relief valve only discharges water when the system pressure reaches the rated pressure . This could be because of expansion . To eliminate this , turn off the electricity supply to the geyser . Water is not compressible so if it is leaking due to expansion it will stop dripping immediately . If it does stop dripping , we have confirmed that it is expansion . When doing this test make sure that there is no solar heater present as this will continue heating the geyser even if the element has been switched off . pressure is not coming from back pressure from an unbalanced feed . This would only be the case if new alterations to the system have taken place .)
Once you have ascertained where the fault lies you can decide what action should be taken . By having done these tests it will eliminate your customer phoning you and having to go back for a follow up inspection that you are not going to be paid for and is going to keep you from helping another customer . You will also gain your customers ’ trust and respect for having done a professional analysis of the system .
Happy plumbing and keep safe . PA
If the valve continues to drip , we need to determine what part of the valve is malfunctioning . The first piece of equipment that we require is the humble Pressure Gauge . Attach the gauge to any suitable point downstream ( after ) the control valve . Check the reading . Discharge some water from the system so that the water pressure returns to the valve ’ s set pressure . Take a reading . If the valve is at set pressure ( see table attached ) but the relief valve is still discharging , the relief valve part of the valve is malfunctioning .
If the valve immediately goes to the discharge pressure it is safe to assume that the port that stops the water pressure at the set pressure is not sealing off . ( Before we open the valve make sure that the extra
“ In most cases the old valve should not have been removed as it was not faulty .”
January 2022 Volume 27 I Number 11 www . plumbingafrica . co . za