No hot water on gravity system?

[macka09]

Hi all. Any suggestion on possible causes?
Trapped air? Gate valve stuck?

 

[Ch4 plumbing]

I'm an idiot and didn't read the post properly!

 

[Leo21]

Hi all. Any suggestion on possible causes?
Trapped air? Gate valve stuck?

You in the trade?

 

[IDCHAPPY]

Air lock would be the most possible option, unless it's controlled by a motorised valve.

 

[Ermintrude]

Nrv stuck open pump filled return on grav with air

 

[missplumb]

air trapped in the cylinder coil

 

[Dannyparty92]

Get a bit of hose pipe go up in your loft and go to the bigest header tank and the pipe that bends over it put the hose pipe in it and suck till you get water out this should clear the airlock. How old is the boiler?

 

[Leo21]

If it's a gravity system it will only be so air lock if it's been drained recently. Most likely cause is a seized ball valve in the f @ e tank. The water is lost through heat evaporation.

 

[macka09]

Sorry folks. This isn't a job I've been to as yet. I'm going to look tomorrow. I am in the trade but still very new to it. As I haven't been to the job I assumed an air lock or the gate valve on the cold feed to the tank is stuck shut.
Someone has changed the ladies cold feed tank which apparently just serves a hot water cylinder I haven't been told anything else.
That's why I thought about getting a little heads up.

 

[Leo21]

It'll be related to the tank change. Al, you need is water and heat to make it work.

 

[macka09]

Ok. I know it's definitely something with the recent work. The vague info I've been given leads me to think a gate valve has failed. I'm sure the chap said he's turned the immersion off.

 

[brum]

Get a bit of hose pipe go up in your loft and go to the bigest header tank and the pipe that bends over it put the hose pipe in it and suck till you get water out this should clear the airlock. How old is the boiler?

good call but it may be a tad easier to cross kitchen taps and blow back mains into hw tap back into tank..brum

 

[macka09]

Is it as simple as putting a hose on the cold tap an opening them both? Never done it before

 

[Best]

If it is just a simple air lock in the hot pipework (probably cold feed to hot cylinder) then just put the cold through the hot. I do it on the bath mixers where the cold & hot are both from gravity (cwt) supply. Even though they are basically the same pressure, if you open the hot tap on a bath mixer & holding your hand over the outlet, just turn cold full on & hold for about 10 seconds at least & air is blasted up the cylinder feed.
Other sure way is to join hot washing machine valve to the mains cold w.m. valve using a w.m. hose.
Or remove the neck from kitchen sink mixer & hold your hand over the hole while turning hot & then mains on. You normally cant keep the neck in as the neck divides the supplies on modern mixers.

 

[Leo21]

Are we taking about no hot water through the taps, or cold water running through hot tap? As in not heating or not running?

 

[macka09]

Not running through hot tap

 

[Leo21]

Not running through hot tap

I shall correct my response to, Gate valve shagged. Got a bung kit?

 

[macka09]

Bung kit?

 

[Leo21]

Rubber cones that you stick up the cold feed and vent. They vacuum the system, so you can change the gate valve with the tank full.

 

[tamz]

More likely to be an air lock as whoever did the work previously wouldn't have left it not running.
Blow the mains up through the hot

 

[kris]

Easy fix if there's a mixer tap with no check valves below , all youl need is maybe a towel to wipe your face dry lol

 

[macka09]

?????

 

[kris]

Put your hand over the spout of the mixer tap and open the hot first , then open the cold , because your hands over the spout it forces the cold up the hot side in turn moving any air , if that's the problem this should help mate, you might get bit spray on your face but it works lol

 

[kris]

If it's the gate valve then there will be spray lol

 

[Reg Man]

No water through the tap? Scaled up hot water outlet on the vessel. Not heating up on the gravity circuit? no water in the primary flow and returns.

 

[Mike Jackson]

More likely to be an air lock as whoever did the work previously wouldn't have left it not running.
Blow the mains up through the hot

You're kidding right? I've had snapped gate valves left by many a previous plumber. Last one was just before Xmas. Shower pump not working properly. It was surging, I diagnosed some sort of blockage and found the gate valve on the cold feed snapped and almost shut but apparently the handyman that did some work when the problem started hadn't touched it! Must be a poltergeist then.

If it is an airlock, easiest way of clearing it is wet vac on the hot tap.

 

[Bolty123]

As previously stated it will be due to recent works. Old vent pipe could be hovering at the water level in the new tank or something daft like that.

 

[kay-jay]

You're kidding right? I've had snapped gate valves left by many a previous plumber. Last one was just before Xmas. Shower pump not working properly. It was surging, I diagnosed some sort of blockage and found the gate valve on the cold feed snapped and almost shut but apparently the handyman that did some work when the problem started hadn't touched it! Must be a poltergeist then.

If it is an airlock, easiest way of clearing it is wet vac on the hot tap.

with you all the way........until the wetvac bit! i bought one about 3 years ago cos of everyone on here telling me it would revolutionise my life. dont know why but i cant bring myself to use it, never have and quite possibly never will.

 

[rocketmanbkk]

Rubber cones that you stick up the cold feed and vent. They vacuum the system, so you can change the gate valve with the tank full.

You bung it in the vent also?
I change a gate valve once but just bunged the outlet in the cwsc. I didn't bung the vent? Was I lucky? I thought bunging the vent may cause the tank to implode? Sure I've read it on here?

 

[tamz]

You're kidding right? I've had snapped gate valves left by many a previous plumber. Last one was just before Xmas. Shower pump not working properly. It was surging, I diagnosed some sort of blockage and found the gate valve on the cold feed snapped and almost shut but apparently the handyman that did some work when the problem started hadn't touched it! Must be a poltergeist then.

Your right enough Mike. Somehow i keep thinking "tradesmen" are not as bad as they actually are :smile:

 

[kay-jay]

You bung it in the vent also?
I change a gate valve once but just bunged the outlet in the cwsc. I didn't bung the vent? Was I lucky? I thought bunging the vent may cause the tank to implode? Sure I've read it on here?

Not if your working upstream of the cylinder. But there is no need to bung vent anyway.

You only bung vent on an f and e tank cos once youve removed a rad valve or section of pipe you have two open routes back to the tank therefore it needs to be vacuumed.

 

[Mike Jackson]

with you all the way........until the wetvac bit! i bought one about 3 years ago cos of everyone on here telling me it would revolutionise my life. dont know why but i cant bring myself to use it, never have and quite possibly never will.

I've cleared loads of air locks with a wet vac. Had one last year which several other plumbers had failed on. I got called out after a fire in a top floor flat. Firemen had turned off the water to the storage cistern in the roof and it had run dry. When it was turned back on the hot water in the basement flat was only trickling. After several failed attempts at backflushing failed the other plumbers had deduced that muck had been drawn into the pipe and it would need cutting out. I checked in the roof space and the modern cistern was fitted with a bylaw kit and properly sealed so I doubted that this was the problem. Thought that the issue was more likely to be an ailrlock in the cold feed to the cylinder. back flushing from a tap will only clear an air lock between the tap and the cylinder and push water up the open vent. I got the Wickes special wet and dry out of the van and attached it to the hot bath tap. A bit of gurgling and off she went.

 

[kay-jay]

I've cleared loads of air locks with a wet vac. Had one last year which several other plumbers had failed on. I got called out after a fire in a top floor flat. Firemen had turned off the water to the storage cistern in the roof and it had run dry. When it was turned back on the hot water in the basement flat was only trickling. After several failed attempts at backflushing failed the other plumbers had deduced that muck had been drawn into the pipe and it would need cutting out. I checked in the roof space and the modern cistern was fitted with a bylaw kit and properly sealed so I doubted that this was the problem. Thought that the issue was more likely to be an ailrlock in the cold feed to the cylinder. back flushing from a tap will only clear an air lock between the tap and the cylinder and push water up the open vent. I got the Wickes special wet and dry out of the van and attached it to the hot bath tap. A bit of gurgling and off she went.

I have one for if I get such a situation. And im Sure I could find a hundred different applications for it. I just seem to have a mental block about it and just carry on doing things the way I always have.

 

[macka09]

Thanks for all the advice. I went to the ladies house today and immediately there was water from the hot tap and the cylinder was full. Although the cylinder was stone cold due the immersion not being on. So I heated the water and all was fine. The customer complained about the pressure but the tank was only 1.5 meters above the cylinder.

 

[kay-jay]

Thanks for all the advice. I went to the ladies house today and immediately there was water from the hot tap and the cylinder was full. Although the cylinder was stone cold due the immersion not being on. So I heated the water and all was fine. The customer complained about the pressure but the tank was only 1.5 meters above the cylinder.

Its the distance between the header tank water level and the draw off point thats important.