Combining feed and vent piping from F and E tank

[Rudolph_Heller]

It would save me a lot of faff if it was acceptable to combine the feed and vent in the manner shown in diagram below.
Or should I resort to separate pipes for each, as small sketch.

Boiler is Potterton Suprima




I would be grateful for your advice.

Thanks

Rudy

 

[SJB060685]

Combined vent and cold feed is more common than you imagine. As long as its a minimum of 22mm you'll be fine.

 

[Rudolph_Heller]

Combined vent and cold feed is more common than you imagine. As long as its a minimum of 22mm you'll be fine.

Thank you for your prompt reply and yes, it is 22mm.

 

[NewStart]

Combined vent and cold feed is more common than you imagine. As long as its a minimum of 22mm you'll be fine.

Given there's not a check valve in the outlet of the F&E tank I've never understood the need to the vent.

 

[SJB060685]

Thank you for your prompt reply and yes, it is 22mm.

No worries buddy. The only thing I will say about that particular design is sometimes it can prove problematic filling the system from empty and displacing the air

 

[Jim Goodenough]

No worries buddy. The only thing I will say about that particular design is sometimes it can prove problematic filling the system from empty and displacing the air

I always make sure the cold feed is sloping slightly upwards on the 'horizontal' part of the pipework towards the F&E tank, to ensure the air escapes. There's then no real need for a vent pipe back into the tank (saves pipe, insulation and the faff of cutting the lid.

 

[Last Plumber]

It would save me a lot of faff if it was acceptable to combine the feed and vent in the manner shown in diagram below.
Or should I resort to separate pipes for each, as small sketch.

Boiler is Potterton Suprima


View attachment 44993View attachment 44994

I would be grateful for your advice.

Thanks

Rudy

In my opinion, you would be better to pipe it correctly if you can do.

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Given there's not a check valve in the outlet of the F&E tank I've never understood the need to the vent.

Primary open safety vent.
The purpose of the primary open safety vent is to provide a safety outlet should the system overheat due to component failure and ensure that the system is kept safely at atmospheric pressure. The minimum diameter of the safety vent is 22 mm and the pipe should never be valved. In a fully pumped system, the primary open safety vent should usually rise to a minimum height of 450 mm above the water level in the F&E cistern. This allows for any pressure surge effects created by the pump. The open safety vent also aids the removal of any air that the system might collect, particularly on commissioning or refilling.
(Level 2 Plumbing Pearson Schools and FE Colleges)

 

[SJB060685]

I always make sure the cold feed is sloping slightly upwards on the 'horizontal' part of the pipework towards the F&E tank, to ensure the air escapes. There's then no real need for a vent pipe back into the tank (saves pipe, insulation and the faff of cutting the lid.

The continuous rise will help with displacing the less dense air for sure mate. And yes I have seen systems without the vent over hanging the cistern. As long as there's an unrestricted and suitably sized pipe it will work fine.

 

[gmartine]

Seal it.

 

[Rudolph_Heller]

Thank you all for your replies and advice. I will go with the combined method (with inclined feed pipe) for now and see how it works out.
I do however have a question on the "traditional right way" as Last Plumber reccommended. What difference does it make if the feed enters the pipe to pump from the bottom rather than top?
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I think I have the answer to my own question....so that any transient air bubbles escape through the vent rather than feed..

 

[townfanjon]

Not all manufactures advise combined F& E pipes .

 

[Warmiger]

Can you not do away with the tank and pressurise the system? Less corrosion and no tanks to worry about. We generally take the tanks out these days.

 

[SJB060685]

The loop you mention is to limit the amount of heat lost up the cold feed.
Sealed systems can still sludge up if not installed properly and without the neccessary means to vent trapped air and dissolved oxygen within the water

 

[John.g]

Agree with improper installation especially the expansion vessel which is often installed with the filling pressure equal to the pre charge pressure thus leaving no reserve and leading to frequent top ups but also encouraging IMO,that friend of the rad manufacturers, the Auto fill PRV where one has no idea of any developing leak.
Of course the same can be said of the F&E tank with ballcock fill, I have a isolating valve on mine and keep this permanently shut except to check for any leaks by opening it a few times per year and in over 40 years I have yet yo hear it adding a drop of water, strange?. I also have a combined cold feed and vent installed when new, the vent is carried on up over the tank, I still have some of my original installed rads.

 

[Rudolph_Heller]

Not all manufactures advise combined F& E pipes .

The manufacturer's install manual actually shows it as combined, albeit a quite rudimentary diagram, but thanks for your input.