I have an oil-powered boiler along with a water cylinder which has been installed in our home for a number of years by some previous owner. We've been here a couple of years without a hitch.
Just the other week the tundish started overflowing with water every time the boiler fired up. I called the plumber out as I know nothing about boilers or water heating whatsoever, and after having two plumbers out over two days, they eventually told me I need to call someone who clears out drainage.
I'm only just figuring out how the whole system works but I'm hoping someone can explain it a bit more for me.
From the top of the cylinder down to the tundish there's a pipe. The overflow isn't coming from the cylinder. That took me a while to figure out, and was the first thing I thought was happening. The water is actually coming from the bottom upwards. You can see in the following picture that the pipe goes in two directions. Going downwards is from the boiler, and going upwards is…. I haven't got a clue! I can't actually see where it goes unfortunately.
In the following picture you can see the whole setup, the tundish and cylinder on the left, and boiler on the right.
The final picture shows the pipe that goes up to the tundish from the boiler. As you can see, the pipe comes out the very top of the boiler.
My question is, what could cause water to come up from the bottom upwards through the tundish? Is it really a case of blocked drainage and all I need to do is get someone who specialises in drainage out?
Best Answer
Amazing it's been a month since I visited this, but I've now had four plumbers, an electrician, a drainage service company, and a previous owner of the home in to figure this out.
Fortunately, the answer lay in phoning the previous owner who was very helpful.
The outflow pipe is blocked (still) meaning that the excess water which is pumped out from the boiler, and perhaps the cylinder, can't escape to the drain. The drain is somewhere under some bricks that look as if they're cemented in, however some are loose and beneath them is a drain. Yes, you heard right, a drain under some paving.
The answer is to find this drain, which I'll find in the next couple of days, and unblock it by calling a drainage service out to use special tools to clear the pipe work. Basically when the boiler is on, the outflow pipe fills up and up until it comes back up the pipe and into the tundish overflow, leaking out all over the floor.
When in doubt, find out where your overflow goes. When you have no idea where it is, phone the previous owner.
Now I'm stuck with many plumbers bills.