• Welcome to PlumbersForums.net - The international free plumbing advice forum. Professional plumbers sharing advice with fellow plumbers and DIY alike. Register for free today! - Checkout the Plumbing Advice forum and then our Plumbing Videos area which still needs populating.


In geometry, topology, and related branches of mathematics, a closed set is a set whose complement is an open set. In a topological space, a closed set can be defined as a set which contains all its limit points. In a complete metric space, a closed set is a set which is closed under the limit operation.
This should not be confused with a closed manifold.

View More On Wikipedia.org
  1. S

    Closed loop pressure increasing

    Just wondering if anyone has even seen an issue with the pressure gradually increasing on a closed loop system where there is no fill loop attached. I'm seeing this issue on a gshp and whats more unusual is its on the cooling side. If it was on the heating side you could put it down to expansion...
  2. B

    pressure very high. all radiators on even when trvs closed.

    hi all some advice combi boiler is heating water and heating comes on fine. its an ecotec plus - vaillant Issue - Pressure is way to high, sits at 3.3 and goes right up to 3.7 when on. im worried something bad will happen soon. im not sure when it started, but been like this for a month or...
  3. M

    URGENT Stopcock valve leaks when closed but nothing when open

    Hi all, I have a query in relation to stopcock valves for the main cold water supply into the flat just before the water meter inside the flat. I noticed that when closed it’s dripping slightly at the stem, however, when I open it fully again it stops completely. I have checked this for a...
  4. G

    Radiator valve stuck closed (Not TRV)...

    Hi, I would appreciate a little help. I am unlucky enough to have an 8mm microbore gravity fed indirect central heating system (11 Radiators) on a 30 year old free-standing floor boiler. The radiator valve/lockshield are the twin entry type (8mm). All the radiators are fine except for two: a...
  5. B

    Hello. I worked on an oil boiler that when the outside door is closed the burner goes to lockout. When it is opened slightly it works perfectly. Ha

    Hello. I worked on an oil boiler that when the outside door is closed the burner goes to lockout. When it is opened slightly it works perfectly. Has been working fine in same situation for 20 years. I replaced the gasket at the burner and replaced the fire board on heat exchanger access door...
  6. S

    2 Port Valve Closed Question

    I have a honeywell 2 port valve to the emersion tank which is allowing water to pass through on the closed position meaning the water is boiling hot. A previous plumber left an old port valve in cupboard which I took to bits to see how it works. 😀 I thought the seal must have gone inside but...
  7. N

    Can a conventional system boiler be a closed system?

    As per the title? I've only ever seen domestic system/conventional system boilers with an F&E tank and combi boilers which are closed systems. Is there any reason a system boiler cant have an expansion vessel fitted and be made a closed system? Or Is there any reason you couldn't install a...
  8. L

    System sucking in air - suggested fix is convert to closed - looking for more info

    Hi everyone, I'm a newbie here, a layperson homeowner, stopping by in desperation to try and get a better understanding of my options regarding a diagnosis. I have a conventional gravity heating system (cold water tank). British Gas put in a new boiler and replaced most of the other bits...
  9. B

    Orkli VZ-2V valve.I can't find info. on this.(normally closed?-Wiring?)

    Fault seems to be an Orkli VZ-2V in a log burner/buffer tank system.The valve is difficult to access & I can't find info.Is this a 'normally closed'valve(open when powered)?Does switch send 230v from grey wire to orange at end of run?
  10. S

    why was my thread closed

    F1 Problem on an Ideal logic 24 combi was closed with the advice "do not fit it yourself" Where did I say I was going to do anything, I just asked a price guide on expansion vessel, nothing more
  11. S

    Towel rail valves open or closed!

    Hi I’ve just fitted a towel rail. Should both valves be open to fill it? And stay open once filled and bleed? Thanks
  12. B

    Honeywell Motorised Valve Not Fully Sealed when Closed

    When I have my hot water on and the central heating is off, there is still a small flow of hot water through the motorised valve for the central heating. There's sufficient flow to slightly warm some of the closest radiators. Does this usually mean a new motorised valve or is there something...
  13. M

    Cannot fill my closed loop heating system

    I am having a strange problem trying to repressurise my closed loop system. I believe there is a (small?) underground leak in the system as the pressure regularly drops. Typically takes a few days So regularly I repressure the loop with a feed valve. There is a pressure meter near the feed...
  14. E

    New closed system losing pressure

    We moved into our refurbished 2 bedroom house 4 weeks ago. All the plumbing and eating is brand new. There is some wet underfloor which is behaving well. There are also 9 radiators which are less impressive. The system has completely lost pressure 4 times already. The radiators need bleeding...
  15. U

    Why cold tap handle can still be turned even though valve is closed

    Hi all, I recently replaced the compression type valves on my bathroom basin as the cold one was leaking and also when you tried to turn it on the handle would do almost a complete turn before the valve would open and water came out. Thought this was a knackered circlip and seemed to be so when...
  16. quality

    Closed Coupled gasket - seal .

    Hi Toilet are not m thing as some may know however I have replaced a fill valve on cistern whilst carrying out other work at a property and the gasket between the flush mechanism and the pan is a little tired. It measure approx 70mm id but all the ones I can seal are for a 1 1/2 thread which is...
  17. M

    HELP! Tub stopper stuck in closed position

    I accidentally jammed the tub stopper and it won't come out, instead of using the level I just pushed it down... Is there any way to fix this without taking all the system apart? Or Do I also just need to get a new waste system for the tub?
  18. DiamondHead

    Leaking radiator on which I closed the valve

    I have a radiator on the landing that was leaking on the right hand end beneath the temperature dial 6 months ago and I was advised to turn the valve on the other end off because I don't use the radiator and it was either that or replace parts. Problem solved. Until now when the valve itself, on...
  19. S

    Loud bangs from boiler after draining system - closed valve?

    Hi I drained my system today as I was trying (and failed) to install new radiator valves. I have just switched the heating on this evening and the boiler suddenly made loud bangs so i hurriedly switched the heating off. There are 2 valves in the loft, one which turned off the water in the...
  20. B

    Motorised valve allowing water flow even though spindle closed

    hi. I removed actuator from motorised valve. Spindle at 12 noon so valve should be closed. However hot is flowing through the valve. I can manually turn the spindle about 20 degrees. Is it possible the gland inside is not turning even though spindle is? Many thanks.