Boiler loosing pressure

Jeepers_Creepers

Oh, and 2.5bar is probably ok, but take care not to go significantly over this as the safety valve could be opened approaching 3 bar.

Kristoffs

Sorry I wasn’t clear. I turned off the flow THEN the 2 for the filter (3 in total). I’m aware 1 would have been enough but as there is 2 why not do both to make sure. 

Jeepers_Creepers

Cool :-)  I was surprised, since you clearly have a good idea of what you're doing.

Jeepers_Creepers

Kristoffs said:

In terms of the bleeding. It is not a lot of air in the towel rail but if I leave it for a month the top rung will be warm rather than hot. I just assumed this was due to water escaping somewhere means air must be getting in. 

Sorry - just seen this.

In a sealed, pressurised system like yours, air should not be able to get in unless, perhaps, the system pressure reached zero. This is due to the simple fact that your system is still at a greater pressure than atmospheric, so air just wouldn't do such a weird thing.

Having said that, it can happen under a couple of unusual circumstances. One is if the leak is on a higher floor level, so at a lower pressure than showing on the boiler gauge. For example, if the boiler's pressure fell to, say, 0.1 bar, then the pipes and rads on the upstairs floor could well be at below zero pressure. Open a bleed screw on a rad up there could easily find air being drawn in.

The other scenario is also with a very low system pressure. The circulating pump drives the water around and around the boiler and rads. By its very nature, the water on the outlet of the pump will be at a higher pressure, and the water coming into it will be lower. Usually with a system pressure of ~1bar, this won't make a jot of difference - puncture a hole anywhere and water will squirt out under system pressure. However, if the system pressure is very low - just above zero - it's quite possible for the pipe to the inlet side of the pump to fall below zero pressure, and therefore 'suck' in air if there's a leak there.

These are unusual scenarios, tho'. If your pressure is comfortably above zero, this just shouldn't happen.

Are you going to try shutting off the rad system again tonight?

Jeepers_Creepers

And if it isn't air being drawn in to your system, then the source of the 'air' in your towel rail can be (a) a burst EV which is seeping its pressurised air into the system water, or (b) it ain't air but hydrogen.  Hydrogen means a rad system rusting from the inside...

If you are brave enough, you could try holding a lit taper in the jet next time you 'bleed'!

westsussexheating

Your boiler can be dropping pressure for a number of causes. Pressure drop may be triggered from a leakage in the force relief valve, and matter in the expansion vessel, air in your system, or a leakage in the boiler pipework itself.

Reasons of a Pressure Loss in Your Boiler

Auto Air Vent Leak in Heating System

Leaking Heaters, Towel Bars and Radiator Controllers are dripping

Radiators Are Full of Air

Soldered Links on the Boiler Have a Leak

The Pressure Gauge on Your Boiler is Defective