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A cylinder (from Greek: κύλινδρος, romanized: kulindros, lit. 'roller', 'tumbler') has traditionally been a three-dimensional solid, one of the most basic of curvilinear geometric shapes. Geometrically, it can be considered as a prism with a circle as its base.
This traditional view is still used in elementary treatments of geometry, but the advanced mathematical viewpoint has shifted to the infinite curvilinear surface and this is how a cylinder is now defined in various modern branches of geometry and topology.
The shift in the basic meaning (solid versus surface) has created some ambiguity with terminology. It is generally hoped that context makes the meaning clear. Both points of view are typically presented and distinguished by referring to solid cylinders and cylindrical surfaces, but in the literature the unadorned term cylinder could refer to either of these or to an even more specialized object, the right circular cylinder.

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  1. C

    Horizontal hot water cylinder install. Does this look correct?

    Anyone out there able to help? Is this correct or are there things wrong and if so what?
  2. C

    Humming from unvented cylinder

    Hopefully someone can point me in the right direction. Before I start I am G3 qualified. As per usual I was asked to rectify a leak on a combination valve. I installed a like for like 3.5 bar valve, all good, however I I checked pressure in exp vessel to find no pressure at all (Never been...
  3. B

    Unvented cylinder won't stop heating up when CH is turned on

    I have recently moved into a house with the following heating system: Traditional boiler (Worcester Greenstar Ri 24 with only one temperature dial and no pressure gauge) Vented central heating (cold tank in loft) Unvented hot water (Excelsior cylinder with pressure gauge plus white expansion...
  4. B

    New thermostatic shower cylinder fitted - now water is not hot enough

    I have a Bristan mixer shower. It started leaking from the temperature control. A local plumber replaced the thermostatic cylinder. It now doesn't leak - but the water is now 15-20 per cent colder than it was before when the temperature is at max hot. Why? What's amiss here?
  5. O

    UK Cylinders ProLite Air twin coil solar indirect unvented 300ltr

    Hello! I have a new Vaillant boiler being installed and will install a new cylinder at the same time. Our installer is recommending a UK Cylinders ProLite Air twin coil solar indirect unvented cylinder 300ltr. According to specs the standing heat loss is 1.80 kWh/24h which seems pretty decent...
  6. P

    Height differential required between an F&E tank and a cylinder?

    Trying to add a shower into a small bathroom, I'm looking at moving my hot water cylinder to the loft. Currently, I have a vented 200L cylinder (in the bathroom) with the principal source of heat being an Economy 7 setup, which gives adequate hot water for our needs. The cylinder also has an...
  7. J

    Very weird set up - is it a primatic cylinder?

    I can't get a consensus on this from four plumbers that have visited. We've been using the system with no prpblems for 7 years - but the cylinder leaks and needs replacing. It's an old and peculiar set up I have onherited after buting my two storey house. I would greatly appreciate any...
  8. T

    Hot water too hot, changed element and thermostat

    hot water tank water too hot, i have replaced the thermostat and element but still the same issue. Th element is housed in a 4" section of pipe fed from the base of the tank to to top of the tank. Any help appreciated. Any advice welcome, Tony H
  9. J


    Hi All, looking for some advice. I have ARISTON CLASSICO UNVENTED INDIRECT CYLINDER ST1 210 which has corroded at one of the main inlets and is leaking water when in operation. This unit is now obsolete and need to source a replacement. Obviously I am aware that I cannot replace the unit myself...
  10. P

    Unvented cylinder wiring

    Hello all I'm replacing 2 unvented cylinder a which are (a) end of life and (b) installed in a way which is clearly not right (no 2 port shut off valve on the heating coils just for a start, and there are other issues). The heating coils are currently controlled with 3 port valves that are...
  11. M

    Cylinder feed and vent

    Have a ground floor hot water cylinder, want to boost hot flow to upstairs bath with inline booster pump. Can't get to pipework near bath, so wondering if I create a new dedicated vent tee'd into pipe just after it leaves the cylinder, then install pump after new vent, and cap off old vent at...
  12. M

    Possible Cylinder or blockage problem

    We had three radiators changed and after this the boiler wouldn't fire. Now we have heating but the no hot water. We have had the Baxi man out and he said we are not covered for the problem. Which he thinks is either the cylinder (which he said may be difficult to obtain the part) or a blockage...
  13. B

    Another Regular Boiler short-cycling on Hot Water problem...

    Hope someone can suggest where I should looking to resolve this one... I have a Bosch 30Cdi regular boiler on an S plan system with a 180L vented, indirect hot water cylinder. Boiler Temperature is set to 5 (67c) and the stat on the Hot water cylinder is set just below 60c. A Honeywell DU144...
  14. J

    Vent pipe size for vented cylinder installed in 2005-6

    Hey, having searched this forum and last building regs (2000) from around that time... Any idea what the correct size is for a vent pipe for a vented hot water cylinder, gravity fed? I.e. the one that is continuously rising back up to the cold water feed tank for the cylinder? Have discovered...
  15. H

    Unvented cylinder for ASHP

    Hi all. I have an Isoflo CL170 cylinder with good few years life left in it in my system which has performed trouble-free other than the odd new immersion element. I'm getting a new ASHP fitted and the installer is recommending scrapping the Isoflo and replacing it with a Secon Trade Heatpump...
  16. R

    Unvented cylinder viability??

    I'm looking at getting an unvented cylinder fitted but want to know if it's viable before even getting a quote. My cold incoming main is only 15mm but I do get a good pressure and flow which doesn't change alot when another tap or shower is used. Would an unvented be possible?
  17. euge595

    URGENT Motorized valve or cylinder thermostate

    Hi, I have no hot water unless I put the CH on, I've changed the HW motorized valve which still needs to be opened manually and I've changed the cylinder thermostat, can anyone suggest my next course of action. Many thanks
  18. G

    Can I add a seperate header tank to a fortic cylinder?

    Hi I just bought a house with a combination hot water cylinder & cant replace the heating system yet as we have walls to knock down etc where the new radiators would be & the new layout will require different sizes. My GF needs a more powerful shower its a trickle atm. I ordered a pumped power...
  19. B

    Placement of a copper Cylinder for best effect

    I Cannot installa unvented cyclinder because my waterflow rate is too low. I am therefore thinking of using the old attic tank feeding a cylinder system. My query is, Which is the better of two cylinder placements. Water fed to a cylinder in the loft with hot water fed from top of cylinder...
  20. M

    Continuous noise from indirect water cylinder

    I have moved into a house with a Joule Cyclone CY200L indirect cylinder in my loft. Recently it seems to continuously be making a noise, as if it's filling up or heating up, I'm not sure which. The thermostat on the side is set to 55, when I turn it below 50 there is a click and then the noise...
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