Pumping over query

[Rautospoon]

Hi, I live in a bungalow and have a 17 year old traditional CH system with 10 radiators, a BG Multihead III pump (replaced 5 years ago) and an Ideal Classic boiler (re-located in the loft 4 years ago). The system has been serviced every year by BG.
For as long as I can remember (and certainly before the boiler was re-located) there has been a slight drip outside fron the plastic overflow pipe to the F & E tank which often has warm water in it.
The ballcock in the F&E tank was replaced by BG a couple of years ago, but it made no difference.
I have never seen the water in the F& E tank "up to" the level of the overflow pipe, so could the vapour/steam from the warm water in the tank be "condensing" in the overflow pipe and trickling out ? Sometimes it has dripped after the CH had turned off and not when it was on.
The last visiting BG engineer recommended that I rip out the whole system and install a combi as it was outdated with parts no longer available for the boiler (I was easily able to confirm that all parts were readily available on the internet !). I have no desire whatsover to change my system, which with the exception of this one problem, has always and remains (touch wood) to work perfectly !
A "friend of a friend" is a (private) CH engineer and he had a look and confirmed the system was "pumping over" but when he turned the pump spped setting down from 3 (of 4) to 2 (of 4), it appeared to stop and he also suggested fitting a relacement sealed vessel which would be a reasonably priced solution to solve the problem if it continued. He thought the pump was in the correct position and no problem with the HW cylinder and no obvious incorrect piping (although he did say that the precise cause of "pumping over" can sometimes be hard to establish). He said I would be mad to replace the whole system ! However the next day (and continuing) there was/is still the drip and warm water in the F&E tank.

My "instinct" is to replace the F&E tank with a sealed vessel as suggested.
(The loft is boarded with a handrail, has lighting fitted and has ready and safe access to the boiler and tanks).

Any advice, views, opinions from the "experts" on here would be very much appreciated.

Many thanks.

 

[benny_headland]

get your friend of a friend to raise the vent pipe, Iv had to raise a vent pipe to the rafters befor to overcome pumping over!

 

[Rautospoon]

get your friend of a friend to raise the vent pipe, Iv had to raise a vent pipe to the rafters befor to overcome pumping over!

Thanks for the suggestion. The top of the pipe is presently 19" above the top rim of the F&E tank. There is "head room" of at least 48" above the top of the rim of the F&E tank. Is there a recommended maximum height for the vent pipe in this situation ?
Cheers.

 

[benny_headland]

http://www.ukplumbersforums.co.uk/central-heating-forum/20669-central-heating-pumping-over.html (this is a link to a pumping over issue i had a fuw months back!

genral speaking i dont think its that big an issue raising the vent and from what other plumbers on here have said i dont think it is uncomon!

theoretically speaking by raising the vent, the static head created by the water rising up the vent wil eventually cancel out the pressure from the pump! so it will only go so far up the pipe! tho you may want to concider turning your pump down a notch if you have one that allows you to do so?

 

[diamondgas]

Raising the vent to the rafters will most likely overcome pumping over but doesn't get to the cause IMO .... By the way, you don't want steam/ hot water in your f&e, that kind of indicates other issues. The feed pipe should really have enough water in it to accommodate expansion without the 'hot' water getting to the tank, otherwise you'll have the potential for freshly oxygenated water entering the system every time the heating is on and off!

Personally I'd go with sealing the system if your boiler instructions say you can do so! Really depends on how long the system has been pumping over and whether it is now ready for the increased pressures it could well be subject too!

 

[Js58gas]

If your getting hot water pumping over it could be a restricted airsep or h section, try putting a magnet on this bit of pipework if it sticks onto the pipe I would cut this section out and replace. You may also need a flush

 

[plumbqate]

if its a fully pumped system, the positioning of the expansion and cold feed and the pump are important. where are they sited ?

 

[Rautospoon]

So much conflicting information !

I reckon this has been happening for over 10 years. The pump is in the airing cupboard (ground floor) about 5/6 feet directly below the F&E tank in the loft. The BG Multiheead III pump has 4 settings and it is presently running on number 2. For more details please see my OP.

Cheers.

 

[diamondgas]

So much conflicting information !

I reckon this has been happening for over 10 years. The pump is in the airing cupboard (ground floor) about 5/6 feet directly below the F&E tank in the loft. The BG Multiheead III pump has 4 settings and it is presently running on number 2. For more details please see my OP.

Cheers.

You will get conflicting info rautospoon as there's are different levels of experience floating around here and differing work arounds learned over the years ... In my experience when looking at the possible causes I like to know where the feed and expansion pipes are situated, how the pump, f&e tank and bypass are configured and how the system has been piped up in general! From there you have a better overview of the workings of the system ... Not something easily achieved in a few lines on a computer screen! A drawing could possible assist?

 

[dfitz1]

reading some of the comments, some true however by increasing the hight of just vent pipe may not stop this problem. check first that pipe work lay out -from boiler to pump, then cold feed,then within 6'' vent. a part blockage in the cold feed could also cause this problem. water is lazy and will always go the easiest route

 

[Rautospoon]

You will get conflicting info rautospoon as there's are different levels of experience floating around here and differing work arounds learned over the years ... In my experience when looking at the possible causes I like to know where the feed and expansion pipes are situated, how the pump, f&e tank and bypass are configured and how the system has been piped up in general! From there you have a better overview of the workings of the system ... Not something easily achieved in a few lines on a computer screen! A drawing could possible assist?

Will take a couple of photographs this evening, of the configuration in the airing cupboard and the loft, and post.
Cheers.

 

[diamondgas]

Just a thought rautospoon; you could also check out the mi's to see if your boiler can be piped with a combined feed and pipe configuration... That'll overcome any pumping over issues and will not put the system under the additional pressure a sealed system would

 

[Rautospoon]

Just a thought rautospoon; you could also check out the mi's to see if your boiler can be piped with a combined feed and pipe configuration... That'll overcome any pumping over issues and will not put the system under the additional pressure a sealed system would

The boiler is an Ideal Classic which is 17 years old and I only have the User's Instructions not the Manufacturer's (Installer's) Instructions. A few photographs attached which may better illustrate the set up.
Cheers.

 

[Js58gas]

First I would check the cold feed and open vent section for restrictions. I deal with a lot problems like this and 9 times out of 10 there is a restriction around this area and also with the age of the system there is bound to be a restriction there.

 

[Rautospoon]

Anyone got any comments on the pictures of my system that I posted ?

As I am "on contract" with them, I have arranged for BG to come out again. on Monday. I 've requested that they send their "top pumping over expert" !!
Will mention all the useful comments made on here and report back on their conclusions.
Cheers.

 

[diamondgas]

Rautospoon ... hmmmmmmmmmm!

The two 15mm plastic pipes going off to the right on the boiler picture!!! Extremely dodgy! Where do they shoot off to? Don't say the f&e tank? Actually it doesn't matter coz they're dodgy. Should have nothing before the pump on the primaries except the feed and vent pipes and they should both be connected to the flow pipe in a position that allows for air to be vented and about 150mm apart! Air doesn't go sideways unless it's pushed
Next would be the position of the pump. It'll work okay but fitting one pumping down over is bad practise IMO ... clearing air is a big issue!

What model Classic is yours? It looks like an FF but what one I wonder?

 

[Rautospoon]

Rautospoon ... hmmmmmmmmmm!

The two 15mm plastic pipes going off to the right on the boiler picture!!! Extremely dodgy! Where do they shoot off to? Don't say the f&e tank? Actually it doesn't matter coz they're dodgy. Should have nothing before the pump on the primaries except the feed and vent pipes and they should both be connected to the flow pipe in a position that allows for air to be vented and about 150mm apart! Air doesn't go sideways unless it's pushed
Next would be the position of the pump. It'll work okay but fitting one pumping down over is bad practise IMO ... clearing air is a big issue!

What model Classic is yours? It looks like an FF but what one I wonder?

The boiler is an Ideal Classic NF40. The plastic pipes to the right of the boiler (which was moved "straight up" to the loft from the garage directly below when I had the garage converted into a living room about 4 years ago) go to a radiator fitted in the former garage directly below. The "pumping over" problem existed long before this radiator was fitted and (touch wood) neither the pipes nor the radiator they lead to, have given any problems whatsoever, other than I have to turn that radiator off in the summer (when on water only) to prevent it getting hot. I think "from memory" plastic pipes were used to possibly avoid drilling through concrete.
You mention, regarding the pump, "fitting one pumping down over " - what does that mean precisely ?
As previously stated my system (other than this "pumping over" problem) has performed perfectly over the last 17 years and I have no desire whatsover to replace it.
Thanks for your continuing assistance.

 

[fuzzy]

So much conflicting information !

I reckon this has been happening for over 10 years. The pump is in the airing cupboard (ground floor) about 5/6 feet directly below the F&E tank in the loft. The BG Multiheead III pump has 4 settings and it is presently running on number 2. For more details please see my OP.

Cheers.

arrh, where is the feed vent and pump then? that is the issue

 

[fuzzy]

cannot see from your photos where the feed and vent join, prob above pump, can u take another photo, is there an airjeck? maybe they are in the complete wrong position and thats why the probs, where is boiler in relation to cycling, below?

 

[Rautospoon]

cannot see from your photos where the feed and vent join, prob above pump, can u take another photo, is there an airjeck? maybe they are in the complete wrong position and thats why the probs, where is boiler in relation to cycling, below?

Sorry, but don't understand - what are "airjeck" and "cycling" ?!

 

[diamondgas]

Hi Rautospoon,

As asked by fuzzy, where do the header tank feed and vent pipe connect to the system? A photo of those would help... It is there relative position in conjunction with the pump that determines pumping over issues!

Regards the pump pointing down over ... Just bad practise IMO.... Any large amounts of air tend to stop circulation as the impeller spins freely moving nothing!

Regards the radiator ... It will work but is piped wrong and will reduce circulation through your boiler!

Regards your boiler .... it cannot be fitted to a sealed system or combined feed and vent system. However in the instructions you can fit a 'surge arrestor'. Seen it done a few times Hopefully this image will help you understand what I'm talking about if it uploads okay

 

[Rautospoon]

Hi Rautospoon,

As asked by fuzzy, where do the header tank feed and vent pipe connect to the system? A photo of those would help... It is there relative position in conjunction with the pump that determines pumping over issues!

Regards the pump pointing down over ... Just bad practise IMO.... Any large amounts of air tend to stop circulation as the impeller spins freely moving nothing!

Regards the radiator ... It will work but is piped wrong and will reduce circulation through your boiler!

Regards your boiler .... it cannot be fitted to a sealed system or combined feed and vent system. However in the instructions you can fit a 'surge arrestor'. Seen it done a few times Hopefully this image will help you understand what I'm talking about if it uploads okay View attachment 4203
View attachment 4202

Can't find where the header tank feed and vent pipe connect to the system, but I'm not really sure what I am looking for !
Few more pics attached but not sure they will help ?
View attachment 4209View attachment 4210View attachment 4211View attachment 4212


Regarding the "surge arrestor", is this a "bought" or a "made" item ? Can you confirm that this will remedy the "pumping over" problem despite the "root cause"(whatever that might be) not being identified and remedied ?

 

[diamondgas]

I can't access your pics ... however without knowing where the two main pipes in question are connected the surge arestor will not fix pumping over, especialy if it's a constant flow of water! The pump is raising the 'head' of water to a level above the height of your vent pipe if the flow is constant. A surge arestor isn't there to prohibit that.

 

[Rautospoon]

I can't access your pics ... however without knowing where the two main pipes in question are connected the surge arestor will not fix pumping over, especialy if it's a constant flow of water! The pump is raising the 'head' of water to a level above the height of your vent pipe if the flow is constant. A surge arestor isn't there to prohibit that.

No idea why you can't access the pictures - I can, with no problem.

The flow is in no way constant. There is only ever a max of about 3 inches of warm water in the F&E tank which has never risen to the level of the overflow pipe of the F&E tank. The slight drip outside seems to be being caused by condensate forming in the overflow pipe from the warm vapour in the F&E tank.
Just out of interest I have now located the Installers Instructions for the boiler on the internet.
My "gut instinct" is that it is a small problem (if anything serious I reckon it would have escalated itself before now, in the 17 years since the system was installed) that is causing this - the difficulty being in precisely identifying what - will see what the latest visit of BG on Monday brings. As previousl stated the whole system works perfectly (all radiators get hot quickly from top to bottom, loads of hot water that quickly heats up, pump and pipewok not noisy etc.) with never a problem, other than this "pumping over".
Would turning the pump (BG Multihead III) down to 1 of 4 (it is presently set at 2 of 4) be "worth a go" ?
Thank s again.

 

[diamondgas]

Rautospoon .... Just re-rad the posts to see where "pumping over" was mentioned ... 1st post, your friend of a friend mentioned that it was happening and duly noted no longer happens with the pump on a lower speed. Your theory of condensation in the overflow pipe has some credence The fact that the water gets warm is an issue however as it shouldn't in theory. Most likely cause, if not pumping over, is surging up the vent when the pump switches off or a very short cold feed pipe allowing expansion water to enter the header! To over come these two you increase volume. The volume of the 'air' gap if surging and the volume of water in the cold feed pipe if it's expansion...