Diagnosing a blocked cold feed

[SlowLearner]

Hi

This is my first post and I'm very new to the world of plumbing.

I have an open vented system and I appear to have air gurgling in the pipes. I can only hear it when the hot water is switched on, it's all nice and quite when only the heating is running (not sure why this would be?). There is an automatic air vent fitted just past where the hot flow goes into the water tank coil, but it looks all clogged up and I doubt it's working.

From reading posts here I gather that one cause of air in the system can be a partially blocked cold feed, so I'm trying to work out if that's the problem. I held a jar of water up to the vent pipe over the F&E tank, and when the pump came on it took in a little water from the jar, but then spat it straight back out again. I wasn't sure what to conclude from that?

I have also now got a magnet and am going to run it over the cold feed in the airing cupboard to see if I can feel a blockage.

But it occurs to me - I recently bled all the radiators successfully. If all the air got out of them, and they are nice and warm now, would that be evidence that the cold feed is working reasonably well? i.e. air goes out, new water comes in from the FE tank?

Very grateful for any input.

 

[Hugh Jaleak]

Tie the ballvalve up in (or shut the supply off to) the F&E cistern, draw some water off out of a drain off, and see if the level in the tank drops before doing anything else. Some systems do gurgle, but its also entirely possible the cold feed is fine but there's a total or partial blockage in the cylinder coil or pipework nearby.

Secondly if the air vent isn't working it wont be releasing anything as it was designed to do, so needs replacing either with the same or a manual vent. What's the inhibitor situation with your system, does it have any in it?

 

[SlowLearner]

Thanks for the reply Hugh.

I'll draw off some water and check what happens with the F&E cistern. I'm afraid I don't know whether there is any inhibitor in the system, I only bought the house fairly recently.

I forgot to mention that the hot water heats up just fine, there don't appear to be any ill effects of the gurgling in that respect.

If it turns out the cold feed is okay, my plan is to put some Sentinel 400 into the system for a while and hopefully tackle any other blockages that way. I also have a new air vent standing by to install once I've drained the cleaner out of the system. I'll also add some inhibitor when I refill.

Does that sound sensible or is there anything else I should be thinking about?

Thanks again.

 

[J_N30]

I personally run Fernox F5 through the system for 2 weeks, drain then add F1 but it's personal preference.

 

[J_N30]

Also adding system filter such as a magnaclean would be a good idea.

 

[SlowLearner]

Well I tested the cold feed by tying up the ball valve and draining a basin of water from a downstairs drain cock. The water level in the F&E tank dropped, so I guess the cold feed isn't a problem. And in fact the water that came out was crystal clear, which really surprised me.

Given that the water I drained out was clear, is it a waste of time adding cleaner once I've refilled? Or could I expect a cleaner to loosen up a lot of hidden gunge?

 

[SlowLearner]

Also adding system filter such as a magnaclean would be a good idea.

Thanks robo123, I'll look into adding a filter too.

 

[and1c]

It will be clean usually until the system is drained nearly empty. As mentioned, a magnetic filter is a bonus. You need to get the system fully hot before draining ideally, it flushes much more cr*p out.
however, beware, if you have microbore pipework you can end up with blockages you didn't have before.
Also, if you have a primatic cylinder (and only one large tank in the loft) then read up on adding chemicals. .. it's a bad idea IME

 

[SlowLearner]

It will be clean usually until the system is drained nearly empty. As mentioned, a magnetic filter is a bonus. You need to get the system fully hot before draining ideally, it flushes much more cr*p out.

Ah, hadn't realised that thanks. There was me thinking it must be in pristine condition!

 

[Hugh Jaleak]

Maybe worth testing it first, just to check there's no inhibitor already present.