Maximum deviation from horizontal before air lock?

[crosbie]

My system is open vented.

I'm concerned that to avoid "Rise and fall to any degree" would require the use of a theodolite.

I suppose I could pass a run of transparent polythene hose down the intended route, fill it with fizzy fluorescent yellow Gatorade and see which end bubbles drift toward, and whether or not they coagulate into CO2 pockets (assuming the ability to inspect the full length).

However, it seems it would be easier if someone could authoritatively state that a rise & fall in pipework of an open vented system (with say 1m head, and a 5m head circulator) only leaves residual air pockets at h cm, and is not liable to cause an air lock until H cm.

Given such figures I would then have an idea as to just how careful I'd have to be - or not (preferably).

 

[Last Plumber]

There is no need to sarcastic !

I'm telling you my opinion on what you're asking. If you cant tell if a pipe is out of level without your polythene hose, perhaps you be better off getting a plumber in ?

There are reasons for not having high points.

If you do have them, you may ( as I already said ) get away with it. You may not.

Why don't you start the ball rolling by telling us how high H is ?

If you are running under a floor clipped to the joists for example, I wouldn't bother getting a spirit level out but I wouldn't go up and over the girder you mentioned without a vent !

Any air pocket on an open vented system could cause an issue.
There are no "this size of air lock is OK " tables.

 

[crosbie]

I agree that there's no need to be sarcastic (I intended none). I'm not here for a flame war, but for informed advice & opinion.

I agree that any air pocket could cause an issue, and that no size of air lock is ok.

It's at what height of rise & fall that these things occur that's the mystery. :-/

 

[crosbie]

[spurious duplicate]

 

[joni os]

Last Plumber has given a good answer. Water will take the course of least resistance around a circuit. In your case, resistance to flow through first rad will effect capacity to remove air from high point further along system. Good practice avoids high points or incorporates vents.
Theodolites will give both angle and elevation but are inappropriate for the task.

 

[crosbie]

Yes, good practice avoids high points, so in pursuit of good practice (and a lack of problems), I need to know what a 'high point' is in terms of rise & fall height, and how high a high point has to be that a vent should be incorporated where one occurs.

 

[Last Plumber]

I agree that there's no need to be sarcastic (I intended none). I'm not here for a flame war, but for informed advice & opinion.

I agree that any air pocket could cause an issue, and that no size of air lock is ok.

It's at what height of rise & fall that these things occur that's the mystery. :-/

I agree that there's no need to be sarcastic (I intended none). I'm not here for a flame war, but for informed advice & opinion.

I agree that any air pocket could cause an issue, and that no size of air lock is ok.

It's at what height of rise & fall that these things occur that's the mystery. :-/

There is no set height. Each system ( although a lot use the same design ) is unique.

They will all behave slightly differently.

Different rads/emitters, pipe sizes, the number of fittings and bends, lengths of tube, valves, boilers etc, all have differing flow rates and frictional resistances to contend with amongst many other things. Therefore, there is no "rule of thumb" for poor practice being acceptable. It's best not to try.

If it is not level or rising to a vent point, it will collect air/gas.

 

[joni os]

Shutting down rads. or back filling at mains pressure are both solutions to remove air and promote flow. How these are defined by "lack of problems".will relate to the definition you are seeking.

 

[crosbie]

Thanks for the tips. I knew about the mains filling one, but shutting down rads to maximise flow through certain parts of the circuit is a good one.

As to the key heights, unless someone with the requisite figures or formula posts them (eventually), I guess it may be a matter of setting up an outdoor experiment with a 2m high tank of coloured water, and transparent 15mm dia polythene pipe strung out over the ground with 'rises & falls' of varying heights. Then one can see at what heights air-pockets remain, and what height of rise & fall prevents flow entirely.

Place your bets...

 

[crosbie]

For the experiment, I should add that as the circuit is at 1m head pressure, then the supply tank (simulating a circulator of 5m head) would have to be at 3-3.5m and the end of the pipe would have to go up from the ground to a 1m high outflow.