Help needed to understand the purpose of another pipe and valve for expansion tank

[papaya]

Evening guys,

I'm slowly learning how my central heating system works and I would like to ask for your help to understand the purpose of the pipe and valve used with my expansion tank as I can't see the point there :disappointed:


I understand that the white pipe (bended) is overflow and the one with green insulation is the cold feed to the F+E and the other high paper clip type pipe is the expansion pipe for extra protection as all water through it will eventually drop back to the tank BUT I don't seem to understand the one on the right with the valve (circled).



The reason is that this valve controls the water from expansion tank to flow with the hot water from the left through the heater pump. If I turn it off, just the hot water from left will come through to the pump but if I turn it on, it will mix with the hot water comes from left and results in only cold water come through the pump. So what's the purpose of that and should I leave it on or off? I know it sounds stupid but I can't figure out why...


In addition, I would also like to know how could I check if the copper coil in my water cylinder has pinholes?

Many thanks! :blush5:

 

[diamondgas]

Re: Help needed to understand the purpose of another pipe and valve for expansion tan

Thanks diamondgas. .... he said my cylinder keeps generating air to the whole system because of damages in the coil so it cannot be properly solved unless the cylinder is replaced. ...

Thanks again,

That is absolute ball cocks IMHO It sounds like you have circulation problems most likely associated with the configuration you show in your pictures. As Danny suggests, get a second opinion. Without checking the functionality of your pump and valve it's difficult to give advice. One thing to consider and maybe discuss with an 'expert' would be sealing the heating system or at least combining the feed and vent to overcome the possibility of air ingress. Depending on the state of the system will determine whether any further work such as a flush would benefit your system? As mentioned, put up a request on here and at least you can check out to some degree the person's credentials before contacting them ... [DLMURL="http://www.ukplumbersforums.co.uk/im-looking-plumber-gas-engineer/"]I'm looking for a Plumber or Gas Engineer[/DLMURL] ​

 

[Gerard17]

Re: Help needed to understand the purpose of another pipe and valve for expansion tan

Just put a combi in

 

[papaya]

Re: Help needed to understand the purpose of another pipe and valve for expansion tan

Many thanks everyone for your advice and suggestions. I will ask for a plumber here

 

[Dannyparty92]

Re: Help needed to understand the purpose of another pipe and valve for expansion tan

What are the regulations on service valves on heating cold feeds? And I know it's wrong as a few of you have mentioned but why is it wrong? Because most heating systems have gate valves on the cold feed just not as close to the f and e tank.

 

[WHPES]

Re: Help needed to understand the purpose of another pipe and valve for expansion tan

I came across a double check valve on the (15mm) vent pipe of a F&E cistern recently signed off by a building inspector!!!

If not already mentioned, OP your water level in the cistern may be too high. When cold the fill valve should shut off when the water level is about 10cm. Too high and there's not enough room left for water expansion and it will overflow and top up with fresh when cool, causing rapid corrosion.

If you have overpumping, I would recommend conversion to a sealed system if it is appropriate and suitable for your circuit.

 

[deacongas]

Re: Help needed to understand the purpose of another pipe and valve for expansion tan

My guess would be the valve was thrown in for a power flush. coupled with push fit 22mm stop end on vent pipe seals the system temporarily for flushing. not a great idea to leave the valve attached just in case somebody decides to close it off though...doh!

 

[Mike Jackson]

Re: Help needed to understand the purpose of another pipe and valve for expansion tan

What are the regulations on service valves on heating cold feeds? And I know it's wrong as a few of you have mentioned but why is it wrong? Because most heating systems have gate valves on the cold feed just not as close to the f and e tank.

There should be no valves between the boiler and the F&E tank to ensure that there is an uninterrupted path to allow for the expansion of heated water. If the valve is inadvertently closed the expansion will take place up the open vent and may spill over into the F&E tank. This will lead to a reduction in the volume of water in the system and can lead to overheating. It's arguably less important with modern boilers as they have an overheat stat but they can still be damaged. On older boilers with no overheat stat it can lead to water within the system boiling.

Think of the cold feed and F&E tank as being equivalent to the expansion vessel on a sealed system. Shutting the cold feed off is like fitting a sealed system with no expansion vessel.

 

[Dannyparty92]

Re: Help needed to understand the purpose of another pipe and valve for expansion tan

Cheers mike Christ iv seen so many systems with gate valves on the cold feed.

 

[Dannypipe]

Re: Help needed to understand the purpose of another pipe and valve for expansion tan

When I power flush I tend to plug the tank with a rubber bung like this:


Not cheap, but won't blow out. I then wet vac out the tank so I don't draw any sludge from inside down the cold feed.

You buy them from Today's tools. Had mine for years.

Here's one link:

Squeeze and Fix Repair Sets - Buyriteuk.com - BuyriteUK

Pricey for what they are though. I didn't pay that much for them.

 

[Mike Jackson]

Re: Help needed to understand the purpose of another pipe and valve for expansion tan

The jet swet ones look very good. They look like they'll fit through the tank connectors with the projections on the inside.

 

[Dannypipe]

Re: Help needed to understand the purpose of another pipe and valve for expansion tan

The jet swet ones look very good. They look like they'll fit through the tank connectors with the projections on the inside.

They do look good but they're really expensive!

 

[Reg Man]

Re: Help needed to understand the purpose of another pipe and valve for expansion tan

My guess is that because this is such a low head system, that its had pumping over problems, so somone has turned the pump down to its lowest setting to prevent pumping over. The draw back to this, is that now there is not enough circulation to get round the radiators.

Best solution is do away with the F&E cistern and convert it to a sealed system with expansion vessel, PRV, Pressure gauge and filling loop.

 

[Dannypipe]

Re: Help needed to understand the purpose of another pipe and valve for expansion tan

My guess is that because this is such a low head system, that its had pumping over problems, so somone has turned the pump down to its lowest setting to prevent pumping over. The draw back to this, is that now there is not enough circulation to get round the radiators.

Best solution is do away with the F&E cistern and convert it to a sealed system with expansion vessel, PRV, Pressure gauge and filling loop.

Yeah you could be on to something there.

 

[Mike Jackson]

Re: Help needed to understand the purpose of another pipe and valve for expansion tan

It could also lead to a world of hurt on an old system.

 

[Dannypipe]

Re: Help needed to understand the purpose of another pipe and valve for expansion tan

Upgrade the feed to 22mm and have a combined feed/vent pipe.

Or move the pump?

Needs looking at and sorting properly.

You could seal the system but doesn't have to be at 1 bar static pressure, could be lower to prevent straining the old system (if that's your concern).

 

[Dannyparty92]

Re: Help needed to understand the purpose of another pipe and valve for expansion tan

reg man? so you mean when the heating is on the pump surges and forces water into the cistern from the vent pipe because the pump is so close to the level of water in the f and e tank?

 

[Reg Man]

Re: Help needed to understand the purpose of another pipe and valve for expansion tan

reg man? so you mean when the heating is on the pump surges and forces water into the cistern from the vent pipe because the pump is so close to the level of water in the f and e tank?

The area before the pump where the open vent and cold feed are, is the negative pressure zone. On occassions of low head systems with high resistant systems. The pump will have to be set quite high to get the circulation. This can cause air in the system and pumping over.

As said before, your options are, Sealed system or raising the F&E cistern and repositioning the pump.

 

[papaya]

Re: Help needed to understand the purpose of another pipe and valve for expansion tan

My guess is that because this is such a low head system, that its had pumping over problems, so somone has turned the pump down to its lowest setting to prevent pumping over. The draw back to this, is that now there is not enough circulation to get round the radiators.

Best solution is do away with the F&E cistern and convert it to a sealed system with expansion vessel, PRV, Pressure gauge and filling loop.

Regman, we have microbores so a sealed system sounds like we will get a little chance that the pipes would burst

 

[Reg Man]

Re: Help needed to understand the purpose of another pipe and valve for expansion tan

Regman, we have microbores so a sealed system sounds like we will get a little chance that the pipes would burst

If you go the sealed option route, then check the condition of the exisisting pipes and valves to make sure there up to slightly higher pressure. 1.5bar = about 15 metre head of pressure (49ft)

 

[Dannyparty92]

Re: Help needed to understand the purpose of another pipe and valve for expansion tan

It would pump over even if the vent is just before the pump on the negative side?

 

[papaya]

Re: Help needed to understand the purpose of another pipe and valve for expansion tan

Dear all,

Thought I should update this thread. First of all, the system is fully working now so I am very happy about it.

I will explain what happened:

I called a plumber in and we decided to replace hot water cylinder first. After removing the immersion heater, we found a serious pinhole leak (should not be called pinhole at this point) at around the coil joint connecting to the water flow pipe. After replacing the cylinder, we tested the system and found it still took very long to heat up. We then checked some pipes near the boiler and discovered that some sections were clogged with red mud like rusts and debris. We tested the circulation with power flush pump and found it worked so we decided to clean the boiler and do power flush (I live in a very hard water area). During the cleaning and flush process, I saw brow mud like dirts coming out from the boiler and dark water from the pipes which indicated how bad the system was. The plumber told me this was the worst 3 year old boiler he had ever seen. After the cleaning was done, all sorted! He also told me that the only explanation about the dirty system is that when previous owner refurbished the whole flat, he did not replace all pipes and do a proper power flush.

Anyway, thanks again for alll of your input and I have learnt so much from your replies.

 

[Howsie]

Help needed to understand the purpose of another pipe and valve for expansion t

Thanks for the update. Sounds like an amateur install to me.

 

[Reg Man]

Re: Help needed to understand the purpose of another pipe and valve for expansion tan

That's great. Glad you got away with power flushing the micro bore, some companies won't do a power flush on micro bore because they end up with a sprinkler system. So all's well that ends well.