Low Pressure Hot Water Float Valve

March 16, 2011 12:57 am Published by
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Gravity feed low pressure hot water

A customer in Ashburton this week had water overflowing from their roof! As it turned out it was coming from an overflow pipe which was discharging from their electric low pressure hot water service in their ceiling space. There was a faulty float valve that was leaking and causing the flood. We replaced the valve and purged the lines to remove airlocks within the hotwater lines. The header tank was flushed and cleaned and the plumbing reconnected. After adjusting the valve to suit the water levels, the customer was curious of the hot water service that they had inherited as they were new owners to the property and were not familiar to low pressure hot water units. So i explained that the low pressure hot water unit that is found in the ceiling of older style homes has a smaller header tank that supplies the cold water feed to the hot water service. Also known as a gravity feed hot water unit, the smaller cold water feed tank is sometimes attached to the side of the hot water unit or it is installed at a higher level above the hot water unit with plumbing to suit. On some occasions the hot water unit can be on the ground floor and the cold feed tank installed high up in the roof space to gain water pressure for the bathrooms. As it is the height difference between the cold feed tank and the taps that makes a difference with gravity feed hot water supply. Which is completely different to a mains pressure hot water unit where it is the pressure of the cold water that pushes the hot water through the unit. In a gravity feed hot water unit there is a cold feed from the base of the header tank to connect to the hot water cylinder and a expansion tube that feeds back up into the top of the cold feed tank. This expansion pipe allows for the expansion of water as it is heated within the hot water service unit to rise in the expansion pipe and discharge to the cold feed tank on occasion. On the side of the cold feed tank is the mains pressure cold water inlet. There should be an isolating stop nearby that can close the water supply to the feed tank for future maintenance. The cold feed from this isolating stop is connected to a “float valve” that is securely fastened to the side of the cold feed tank. The horizontal float valve operates by opening and closing a plunger against a seat through the action of a lever arm attached to a float. The lever arm is interconnected to the plunger via a cam. As the water level drops, the float and lever arm move in a downward direction allowing the plunger to move away from the seat, which opens the valve. When the water level rises, the float and lever arm move in an upward direction and the plunger moves towards the seat until it seats fimly against the seat and shuts the valve off. 

There are a few maintenance issues that do occur with these type of float valves.
1/ Dirt, rust deposits and the like can get caught under the seat of the valve and leak.
2/ Very high water pressure can cause noisy plumbing when filling.
3/ Maintenance of the valve due to replacing washers and in poor water quality areas damage valve seats.
They are generally a very reliable valve where the float arm can be adjusted to suit the water level within the cold feed tank. There are several things to be aware of with these type of heaters.
With all adjustments and maintenance to plumbing they should be carried out by a licensed plumber with the experience to quickly pin point potential problems at hand.
Our customer was looking for a plumber in Asburton and was recommended plumbing in melbourne Newman Plumbing by a neighbour. Plumbers melbourne, Newman Plumbing is a professional licensed plumber in melbourne so if your seeking a plumber in Alphington, plumber in Ashburton plumber in Ashwood plumber in Balwyn plumber in Balwyn East plumber in Balwyn North plumber in Blackburn plumber in Blackburn North plumber in Blackburn South plumber in Box Hill plumber in Box Hill North plumber in Box Hill South plumber in Bulleen plumber in Burwood plumber in Burwood East plumber in Canterbury plumber in Camberwell plumber in Clifton Hill plumber in Collingwood plumber in Deepdene plumber in Doncaster plumber in Doncaster East plumber in Donvale plumber in Fitzroy plumber in Glen Iris plumber in Glen Waverley plumber in Hawthorn plumber in Hawthorn East plumber in Ivanhoe plumber in Kew Plumber in Kew East plumber in Mitcham plumber in Mont Albert plumber in Mont Albert North plumber in Mount Waverley plumber in Nunawading Plumber in Park Orchards plumber in Richmond plumber in Ringwood plumber in Surrey Hills plumber in Templestowe plumber in Templestowe Lower plumber in Vermont plumber in Vermont South don’t hesitate to contact us and arrange an appointment for plumbers Melbourne in the Eastern Suburbs.
An overflowing low pressure hot water service leaking in a ceiling overhead is the stuff of nightmares! They need to be respected and maintained in a proper manner by a qualified professional.

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