Vented system - air separator

[Malc C]

About a year and a half ago we had an issue with our CH system, which had an air separator as shown in the diagram below (although the vent pipe was straight up to the FE tank)

Turned out that the separator was silted up and the point where the 15mm cold feed joined the separator was blocked solid. Things being what it was all efforts to obtain a replacement quickly failed, so I simply removed the separator and connected the pipes as per the diagram below

However, since replacing my pump I've noticed that when the pump starts it sounds like air is bing drawn in the moment it starts, so I'm looking at two possible fixes and would like your oppinions.

The first is to change the Tee where the 22mm feed to the pump from a 22mm - 22mm - 15mm tee to a 22mm all round, and then reduce the 22mm to 15mm 6" up the feed

Or fit a new separator :

 

[lightning]

if you are not going to use a air seprater then the cold feed and vent must be within 150mm

 

[Malc C]

Hi,

Sorry should of put some dimensions on the drawings..

The distance between the feed and the vent is 5cm

 

[ChrisR]

DUn proper:

 

[Malc C]

Chris, thanks for the drawing. Can you explain the advantage / reason the feed from the F/E tank is fitted that way.

 

[ChrisR]

Reduces/prevents convection losses up the pipe into the tank. Bigger loop is better.

ALso worth extending the loop above the tank on the vent, so you don't get odd pulses of water going over.

 

[gas4you]

Personally, I've never had any problems with air seperators. I always use the aerjec on open vented systems and fit these when customers have problems on systems that are plumbed as you now want to change yours to

 

[Malc C]

Dave,

The original must of been there for decades the 15mm outlet was very furred up to the point little or no water flowed. We moved in to the house in 2001, had a new boiler fitted same year (new piping up to the airing cupboard where the cylinder and pump is). I then fitted a new HW cylinder, pump, three way valve and controller in 2003, with complete new pipework and rads undertaken in nov 2007). The separator was removed around June 2007.

Looks like I'll be popping down to my local plumbers merchant to get a new separator then

 

[gas4you]

All the pipe work off new air seperators (aerjecs) is in 22mm, or 28mm , depending on which model you need.

 

[Malc C]

Well I've finally got round to re-plumbing the CH to include the separator.

OK the soldering might not win any prizes for neatness, but it don't leak

So far the system is working fine and we are no longer getting air in the upstairs rads.

 

[namsag]

Had loads of air sep`s block up ,and the trouble is at first you think cant be blocked by the sep but 9 times out ten it is.

GET a board under that tank to support it
ChrisR would you like to double check your drawing

 

[Malc C]

Th picture is a bit deceiving. The tank sits on three hardwood beams that are about 2" thick and 3" wide, the first of which can be seen behind the softwood plank (slightly bowing) that the clothes are placed on.

 

[swbjackson]

namsag means directly under the tank. Plastic cisterns aren't designed to be self supporting, they should have the base fully supported.

 

[Malc C]

Ahh.. Thanks Mike

 

[twgas]

I believe there should be 1·5m vertically from f&e tank to pump, you've probably got 900mm, this can cause air in/water out of the vent pipe.