Plumbing Question

Drained hot water system (low pressure) and now have little hot water,

Large farm house, gravity fed system, took out a mixer shower and fitted an electric one and put stop ends in the hot and cold feed to shower, then fitted a direct from mains supply to the elec shower.
Since we did the work the hot water tap runs at good flow cold, then as the warm water gets to the tap it runs for 10 secs or so and then it runs constant but like its someone urinating (excuse description, but best way to describe) also continues to be hot.
The taps all do the same thing.
It is like the pipes fill with a constant dribble and then once the pipes are emptied there is just the constant dribble.
No heating system is an old storage heater system, we didn't touch that.
What does anyone think?
Mixer tap in kitchen.
If its an airlock would the water still run?

Thanks in advance, could save us hours tomorrow?

5 Answers

Best Answer

hi this sounds like an air lock. only a small amount of water will be getting down the pipe filling it up like you said so works initially but then tails off. there are several ways to clear the air lock. one is to isolate the mains then open every hot tap/shower point in the property until the header tank is empty, then turn on the mains then turn off the down stairs taps as they start to flow then work to the up stairs. two is more fiddly and you will need help, you said you have a mixer tap so what you will need to do is get a rubber glove and a cloth, with the mains water all turned on and all taps closed, put the rubber glove over the spout of the mixer tap blocking where the water comes out and then put the folded cloth over the glove and using your hand apply pressure to block off the spout (be careful and use both hands to steady the spout. get the other person to then turn on the hot water tap you should be applying enough pressure to the spout that no water comes out, then slowly and carefully turn on the cold water (mains pressure) if water squirts out turn off and readjust your glove so none does. turn on the cold tap for approx. 5 seconds this will force its way up the hot pipe pushing the air lock out, releasing the glove allowing the water to flow back out the hot and hopefully pull the water through. if it doesn't work at first try it for 10 seconds then 15 and so on. between tries allow the water to drain out the header tank so you don't fill it up too much. hope this helps and makes sense. oh you could also try sucking the water down the hot tap by using a hose attached and fill the hose then use it to syphon/suck the air lock out . Joe barratt

Answered 24th May 2015


Member since 22 Jan 2009

It could still be an airlock. A simple way to remedy is to open the hot on the mixer tap in the kitchen, wait until it's down to a dribble, then cover the outlet-(where the water comes out of the tap), with your hand and slowely open the cold. Let it run for a short time- be aware if the pressure get too much you will get wet!! What you are trying to do is reverse the hot water flow with cold main water to force out any air. You may have to do it a few times. Good luck. Ed from Planet Plumbers

Answered 23rd May 2015

Planet Plumbers

Member since 23 May 2015

Hi. Check the following

1) Is the hot water isolator by the hot water cylinder turned off?

2) Look in the cold water storage tank, normally located in the loft. There may be debris or a mouse stuck in the outlet pipe to the hot cylinder.

3)Check that the isolating valve is clear of debris and that if it is a gate valve type of isolator that the gate has not broken off in the closed position. Check this by turning the mains off then running the hot tap until it slows and stops. Also open any cold taps that run off the tank as it might take a while otherwise. Take the head off the gate valve, or if it is a lever valve type undo the bottom nut and check for a clear route for the water. Put back together and turn on water.

4) If you have a mixer tap in the kitchen, then cover the spout with the palm of your hand to create a seal. With any luck you don't have a check valve on the hot water. If you know what this is then have a look for one under the sink. Open the hot tap and then slowly turn on the cold. This will back the water through the hot pipe backup into the tank and may clear any airlock or debris.

If this doesn't fix it and no-one else has any other ideas then all I can say is call a plumber. Hope this helps

Answered 22nd May 2015

Bowen Bathrooms

Member since 15 May 2015

It definitely sounds like you have some kind of restriction, when you first turn the water on, the water has had time to build up pressure in the system (which is why it runs well to start with). Connect a hose pipe from a mains fed cold water tap to the hot and back fill the system to remove air, open each of the hot taps in sequence one at a time to ensure water runs out fast. Also check all valves you isolated when first doing the job as the valve plug may have become detached from the handle and so the valve will need changing.

Answered 24th May 2015

AS Architecture

Member since 21 May 2015

No feedback

If it was working prior to the drain down then it is an air lock. Either locate any vents in the high level pipework or back fill the hot water system with a high pressure feed from the cold main.

Answered 22nd May 2015

kevin cassidy building contractors

Member since 16 Dec 2010

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