Water discharging from the loft vent pipe as CH turns off?

[Markw996]

Hi,
I have just moved into my first home, a 2 bed semi-detatched and as the title says I have a very noisy central heating system.

As it comes on I get lots of bubbling / gurgling noises that last about 10 seconds and seem to originate from either the upstairs radiators or the airing cupboard.

Also as the central heating clicks off it sounds like someone emptying a bucket of water up in the loft right above my bedroom (very worrying the first time it happened!).
I traced the loft noise to the expansion tank in the loft where, as the heating clicks off, I am getting about half a litre of water discharging from the vent pipe back into the tank.

The system is open vented circa 1992 and I take the vent pipe to be the one that rises about a foot above the tank, then bends in a U shape back down into the tank.

I've had breif discussions with a plumber friend and he says it could be the boiler thermostat?!? but I suspect it is more likely to be air in the system somewhere (although I am certainly not clued up on central heating systems) as I did have to bleed a lot of air from by bathroom radiator when I first moved into the house due to it being very cold at the top.

Just to summarise:
I have 2 tanks in my loft and the problem is relating to the smaller tank which does the central heating.
My boiler is located in a downstairs cupboard.
My airing cupboard is upstairs and contains an immersion tank, pump, and a motorised valve of some sort.

I hope someone can help as the noises wake me up in the mornings and annoy the hell out of me in the evenings! (

Many Thanks,
Mark.

 

[Reg Man]

Jase158, I take it that we can now disregard your post number 18, and we will go with your post number 22.

 

[marinegmillie]

I think what he ment is where the cold feed and vent is piped to pump, the cold feed is quite direct into pump, maybe pulling in some water hence venting back over to get rid, just a thought.

 

[jase158]

but in a earlier post jase, you said it was wrong, am confused now.

I was saying the arrowed pipe is wrong as it is pumping water through the return? the opposite way that you want it? I have never seen one of these installed like this?
And secondly I have never seen a fully pumped system this way? I have learnt something and it proves that college is absolutely useless, all my diagrams in my books show the vent and cold feed going into the boiler, but the pump should be after the vent and cold feed. Surely there must be another way as this looks to me like it will draw water from the F and E tank.

 

[jase158]

I think what he ment is where the cold feed and vent is piped to pump, the cold feed is quite direct into pump, maybe pulling in some water hence venting back over to get rid, just a thought.

finally somebody who understands, is there no other way that this can be piped up?
And for all those who say that this is ancient plumbing, my plumbing doesnt even have a pump. So pumped central heating only cant be that ancient.

 

[Reg Man]

Jase158, I thinking about sliting my wrist over this thread. There are alot of forum members who have an enormous amount of experience probably some go back to 1960's. The H lay out as it is known has been around since the introduction of fully pumped central heating systems back in the 1970's. It is the only proven method of installation which works and does not cause pumping over on an open system Ect: Give me any manufacturer boiler instructions from this time to current day and it will show this method of piping. Your labeling on the photograph is spot on.

 

[jase158]

Jase158, I thinking about sliting my wrist over this thread.

Thats a bit drastic? I was saying that i was wronge and everyone else is right,

May i just explain a couple things,
1. I have never installed a pump or a full central heating system
2. I am relatively new to plumbing, compared to some of the people on here,
But what i am saying is, just because everybody does it this way and it works this way doesn't neccessarily mean its right, although it is right this time
and isn't there any other way of doing it?

 

[jase158]

Let me just ask a question.
Where the pump connects in does it pull water as well as push the water around the system? or does it simply push the water round?
If it pushes only then obviously this is where i am getting confused, but if it pulls the water, what prevents it from pulling the water from the F and E?

 

[Reg Man]

Thanks jase158, feel better now.

The best leap forward I think, is sealed systems. They don't suffer many of the water quality problems you get on the open systems. Only draw back is the manual top up.

 

[jase158]

Thanks jase158, feel better now.

The best leap forward I think, is sealed systems. They don't suffer many of the water quality problems you get on the open systems. Only draw back is the manual top up.

Doesnt this have to be a new (ish) boiler though, Condensing type or combi? as there has to be a AAV, Expansion Vessel and PRV?

 

[Reg Man]

From post 19 Quote:The concept is worked by locating the open vent a cold feed as close together as possible (within 150mm) on the flow pipe before the pump. The reason it has to be before the pump, is that this area will be the place of the least pressure on the system therefore preventing circulation into the header cistern. Quote:

 

[Reg Man]

Doesnt this have to be a new (ish) boiler though, Condensing type or combi? as there has to be a AAV, Expansion Vessel and PRV?

Not necessarily. I fitted sealed systems back in the 1980's on cast iron boilers. They did have to be fitted with overheat thermostats and manufacturer would have to state it was suitable for sealed systems. The expansion vessel, PRV, Pressure gauge and filling loop were the extra bits we had to install.

 

[RoryD]

You have a blockage, you will need a powerflush and perhaps a reconfiguration (clearly haven't seen the system). I get this all the time mate.

 

[Markw996]

You have a blockage, you will need a powerflush and perhaps a reconfiguration (clearly haven't seen the system). I get this all the time mate.

Thanks, I have a plumber coming to powerflush the system tomorrow afternoon, in preparation of me fitting all new TRVs and a Magnaclean.

I might ask him to fit an air separator at a later date as I can't get my head around the flow & return connections.

 

[tamz]

Jase158, I thinking about sliting my wrist over this thread

May i just explain a couple things,
1. I have never installed a pump or a full central heating system
2. I am relatively new to plumbing, compared to some of the people on here,
But what i am saying is, just because everybody does it this way and it works this way doesn't neccessarily mean its right, although it is right this time
and isn't there any other way of doing it?

Still got a lot of learning to do eh

Let me just ask a question.
Where the pump connects in does it pull water as well as push the water around the system? or does it simply push the water round?
If it pushes only then obviously this is where i am getting confused, but if it pulls the water, what prevents it from pulling the water from the F and E?

If i have time later i will draw you a couple of pictures that will help explain how it works.

 

[philip mc geown]

i agree have been in many an old house with this type of layout, but it is a reconised piping method and many people still use it 2day!

 

[fuzzy]

cannot see how that system works, isnt the return joing on the positive side of the flow, how does the water get round?

 

[fuzzy]

oh its a bi pass i presume, will adding a bi pass valve help?

 

[tamz]

oh its a bi pass i presume, will adding a bi pass valve help?

It is a bypass without a valve. Fitted by an eejit as it is not necessary in the first place and if he fits one, at least valve it.

If the kids don't come through i'll not be doing much tomorrow so i may explain how different systems work with a few drawings.

Clue = neutral point.

 

[efficient]

got to be the best post ive read.... ****ing myself here about you lot arguing over a basic layout. The layout is spot on other than the bypass needs a ABV on it. If there is water coming out the vent pipe then theres got to be a blockage not allowing the circulation hence water coming out the vent its got nowhere else to go..

 

[Reg Man]

got to be the best post ive read.... ****ing myself here about you lot arguing over a basic layout. The layout is spot on other than the bypass needs a ABV on it. If there is water coming out the vent pipe then theres got to be a blockage not allowing the circulation hence water coming out the vent its got nowhere else to go..

Totaly agree. Its basic layout, the only way to pipe up open systems over the years. I think some of the forum posts, got a little consfused.

 

[fuzzy]

It is a bypass without a valve. Fitted by an eejit as it is not necessary in the first place and if he fits one, at least valve it.

If the kids don't come through i'll not be doing much tomorrow so i may explain how different systems work with a few drawings.

Clue = neutral point.

yes tamz it is due to the neutral point, obviously punping over is under positive pressure ie, pushing not pulling, did they suss out the problem? is the pump on the right way? if it was working properly then started to fault there must be a reason. if its been like that from new or since some work was carried out then all fingers point to that!

 

[fuzzy]

just read some posts, yes i agree the layout is VIP and therefore as good as it gets, cold feed is the neutral point and therefore the vent is within the neutral zone and shouldnt pump over all else being correctr. ive seen loads of these blocked at the cold feed.

When waters hot it should expand up the cold feed, if it blocks it wont be able to expand into the F&E cistern and has to expand up the vent. then it cannot come back into the system. its not really pumping over as such but expanding over. saying its pumping over leads people to believe theres a feed and vent fault, without seeing the system in operation its hard to say but i agree cut out the tee and replace would be first check.

fuzz

 

[Bartdude]

What's going on?? What's this ancient system? They don't show this on the course.

I'll tell you what,let's rip it out and stick a combi in

 

[tamz]

The basic principles of system design are being lost due to combi's and sealed systems being more popular bit it should be important to know the basics.
There are dozens of ways to pipe a system all based on a few basic layouts.
Understanding how the position of the feed vent and pump effects the water circulation helps.
Here are a couple of drawings. (this could have been a far longer post but i have simplified a lot of things)

I'll start with this one. Basic common layout for a gravity HW, pumped heating on an old cast iron boiler.



The position of the feed connection to the system is called the neutral point. Everything from the pump to the feed is under positive pressure (from the pump) and everything after the feed is negative.
In this drawing the only part of the system under positive pressure is from the pump to the boiler (as this is effectively the point the feed connects). The rest of the circuit is under negative pressure (the water is being pulled).
Because the cast iron boiler holds so much water it also acts as a neutraliser and the water flow from the pumped side slows right down so has very little effect on the gravity side.
It used to be though having the pump on the return like above would help the gravity circuit. In reality it didn't have any real effect.
A system laid out like this will not draw air or pump over (unless a blockage is introduced).


Same system with the pump on the flow. The heating circuit is now under positive pressure (being pushed). This is the better pump position as pumps can push better than they pull.

Move on a few years and motorised valves are introduced and systems become fully pumped. Still using high water content cast boilers, so we get something like this.

Feed and expansion still connected to boiler so position of the pump does not cause it to pump over or draw air. Pump on the flow so the system is under positive pressure.


Same thing with pump on the return. System under negative pressure.


If you use a low water content boiler or the feed and expansion are taken from the pipework, where or how they are connected starts creating problems.

Pipe it as above and a suction effect is introduced to the expansion pipe and if the pump is set too high it will draw air. Fitted like this to a low water content boiler where the pump speed usually had to be set high this is why a lot of systems fitted in the 80's/90's are full of sludge.
Easy quick way to over come this was to combine the feed with the expansion like this

This stopped the problem as the pump had to pull water from the F&E tank rather than air. It was not ideal though.

So they developed this system

Provided the feed and expansion tees were kept within 150mm of each other, the pump would have very little effect on the expansion pipe. Go much beyond the 150mm spacing and it will pump over.

There are dozens of variations of these layouts. Just think how the position of the feed and expansion will effect the system or introduce blockages and think what would happen.

A bit quickly explained and i have missed out a lot but the basic principals are shown. Hope this is of some use to someone.

 

[tamz]

What's going on?? What's this ancient system? They don't show this on the course.

I'll tell you what,let's rip it out and stick a combi in

They don't show much on the courses because they probably don't fkn know. Combi is the answer to everything

 

[fuzzy]

yuve too much time on yer hands tamz!!! lol
youve pretty much said what i said but with more background, i agree alot of newbies tend to favour combis as its all they know. i dont think its the tutors who are at fault, lazy and/or semi skilled plumbers are

 

[tamz]

yuve too much time on yer hands tamz!!! lol

I know lol

 

[SafeGasInstall]

" i dont think its the tutors who are at fault, lazy and/or semi skilled plumbers are"

don't think you were born skilled .....every one deserves a chance and every one who wants to become pro will go through anything to become pro !!!

Thank you for your time TOM !!!!

 

[Horse]

Gents,
New to this so please be gentle.

I have tonight noticed a small amount of warm water spurting out of the vent / overflow pipe into the FE tank when the pump turns off, in water or heating position. Not a lot less than half an egg cup. Only noticed when overflow started dripping outside.
Looking at the vent pipe outlet which was under water its been there a while. (Blue colour)
I have just recently removed and refilled a radiator during decorating. About a week ago.
I have some brown sediment in the tank but whole system is only 10 years old.
I have read the thread and the position of the neutral pipework looks about right.
What height should the overflow/vent pipe invert be above the water level in the tank?
Mines about 4-5 inches. I have seen 18 inches quoted elsewhere but the boiler installation manual says nothing.
When the pump runs I can see a gentle wafting backwards and forwards of sediment around the FE tank outlet.

Any help/advice/sympathy would be gratefully received.
Horse

 

[SafeGasInstall]

dear horse,
first you need some one to see it or picture would help . you have corrosion starting in your system (luck of having inhibitor) ! have you had any air in your radiators lately any cold spots ?