I have a gas fire in a fire place but need to know what would be the best type of chimney pot to use to allow the fumes to be drawn up the chimney (no liner). The house is a 1950s chalet bungalow and it it has a square chimney with a concrete slab on top with a approx 6" hole in it, also the bricks on two sides below the slab are removed. When we have bad storms water is coming down the chimney and I wondered if there is anything we can add to stop this. Would it be simpler to have a liner and pot fitted and the holes in the chimney sealed, this is what next doors appear to have done
I am not able to advise on the best form of chimney pot to use but make sure it is bird nest and bird proof.Some years ago I nearly succumbed to carbon monoxide poisoning. When the gas fire was pulled from the fireplace 12 dead pigeons were removed from the flue. Carbon monoxide alarms are easily obtainable and are not expensive. Even a correctly installed appliance can go wrong between services so get a CO detector!
Have you had the chimney checked for leaks? Why were the bricks removed from either side, under the concrete slab? Why don't you already have a rain cowl over the 6'' hole in the concrete slab? Is the gas fire suitable for any chimney type?
A liner may not be needed if the chimney is fully sealed and intact from top to bottom. The need for the holes under the concrete slab to be sealed is obvious, but the hole through the slab should already have some kind of rain cover, usually in the form of a metal cowl or hood, to stop the weather getting in.
A smoke test up the chimney would be my first advice on this. Seal all the holes up top, then place a PH smoke test pellet in the fire place opening. If the chimney is working properly you should see smoke anywhere else in the house, that includes up in the attic / loft space.
Now you can remove the cover over the hole in the slab and repeat the smoke test to see if the air is being drawn properly up the chimney. The smoke test must be done with the room sealed, as in closed doors and windows, to make sure the room has enough ventilation to remove the flue gases from the room properly. If you see any sign of the smoke being drawn back into the room while the doors and windows are closed tightly, then you need to install a proper constantly open vent to fresh air for the fire not to poison you.
All the smoke must go up the chimney with the room sealed.
When you satisfy all the above tests, and all seems well and good, you can begin installing your gas fire. After you have the CORGI installer in to do it for you safely, he / she should do a spillage test on the fire again to prove that all the flue gases are being drawn away from the room, and that the fire isn't going to kill you and your family while you sleep in front of the tele'.
If there is a hole "through the slab" I can't see why it should also have the side holes. Are you sure about the hole through being present? A complete top slab with holes round all four sides used to be a common sight on some buildings particularly old Army sites. It stopped rain (and bombs) going straight down. In your circumstances I would remove the slab and modify the brickwork such that the flue ran straight upwards, then fit a chimney pot or flue terminal. A smoke test of the flue before starting would be a good idea as it may have leaks in the structure so require lining anyway.
The chimney is what the house was built with. I beleive the holes in the side of the stack were for coal fires to help the draw. We currently have a gas fire, old fanshioned type four element, fitted to the chimney, I suppose the question is if we brick up these holes on the side of the stack and put a chimney pot in the hole in the slab and some sort of rain cover on the pot will it affect the fire that is currently fitted. The chimney stack goes straight down to the fire and looking down it I can see the back of the gas fire, its about 20ft down. We have a carbon monoxide detector, came with the house, which shows no problems.
It is possible that despite you having had no problems the current arrangement is not compliant with the required flueing standards (and likely never was).
I would modify the the terminal and chimney to comply as outlined in John's posting and have the chimney swept for good measure.
And don't just stick a rain cap on as any such restriction can cause serious flue problems. A small number of devices are approved for use with gas flues, make sure anything you intend using is.
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