How to unblock a Cold Feed pipe for my Central Heating

[HO1]

I found that on draining my system the level of the expansion tank does not change, although water does run out from the drain plug at ground level.

I have opened all the bleed screws in the radiators.

The cold water feed goes direct to the boiler which is a NetaHeat however to gain access to the pipe inlet into the boiler I will have to remove the boiler off the wall which I do not want to do.

The system has been in place approx 20 years and I last drained it approx 2-3 years ago.

Would it possible free the blockage if I connected water to the vent outlet which overhangs the expansion tank.

 

[felix]

Are you proposing to connect mains pressure water to your vent pipe? If you really do have a blockage you could do some major damage that way. I'm afraid I don't have anything really positive to offer right now. To eliminate any possibility of airlock trouble, look for a drain valve on your boiler.

 

[doitall]

Why do you need to remove the boiler from the wall tappings are exposed on the netaheats

 

[ChrisR]

Perhaps his installation, like mine, is such that there is simply no access!

HO1 I have done what you imply a number of times. Though it hasn't always worked, the success rate is about 80%. I don't share Felix's fear of doing major damage unless you pressurise your boiler or radiators with high pressure mains. The pipework in a heating system is capable of holding mains pressure. Certainly a bit of care is appropriate. More in a mo.

If you empty the F&E tank (bale it out and cap its exit) and connect the mains input to the feed pipe (thats the usually 15mm one which leaves the tank) you will if lucky find a great feal of gunge come out of the vent pipe, which you can of course collect in the f&e tank. In the 80% I mention, that clearing has been enough to be able to fill the system.

The procedure is such that if the feed pipe is blocked the pressure doesn't go down as far as the boiler or rads. If it isn't blocked then the pressure doesn't rise.
If you send the mains down the vent pipe, this "safety" isn't there; a blocked feed pipe would mean pressurising the system because the blockage always seems to be in the feed pipe.

Obviously you'd need a tap in your connection from the mains if there wasn't one to begin with, so you would open it a small amount at a time to see what's happening.

Assuming you DO have a stop cock on the input pipe to the ball valve of the f&e, undo the compression fitting on the end of the pipe which comes from the stop cock. That reveals a 1/2" bsp male thread. You can screw the "tap" end of a flexy tap connector on there, and the "pipe" end goes on the top end of the feed pipe. You can od course join flexy tap connectors together in series to make any length.

 

[HO1]

Perhaps his installation, like mine, is such that there is simply no access!

HO1 I have done what you imply a number of times. Though it hasn't always worked, the success rate is about 80%. I don't share Felix's fear of doing major damage unless you pressurise your boiler or radiators with high pressure mains. The pipework in a heating system is capable of holding mains pressure. Certainly a bit of care is appropriate. More in a mo.

If you empty the F&E tank (bale it out and cap its exit) and connect the mains input to the feed pipe (thats the usually 15mm one which leaves the tank) you will if lucky find a great feal of gunge come out of the vent pipe, which you can of course collect in the f&e tank. In the 80% I mention, that clearing has been enough to be able to fill the system.

The procedure is such that if the feed pipe is blocked the pressure doesn't go down as far as the boiler or rads. If it isn't blocked then the pressure doesn't rise.
If you send the mains down the vent pipe, this "safety" isn't there; a blocked feed pipe would mean pressurising the system because the blockage always seems to be in the feed pipe.

Obviously you'd need a tap in your connection from the mains if there wasn't one to begin with, so you would open it a small amount at a time to see what's happening.

Assuming you DO have a stop cock on the input pipe to the ball valve of the f&e, undo the compression fitting on the end of the pipe which comes from the stop cock. That reveals a 1/2" bsp male thread. You can screw the "tap" end of a flexy tap connector on there, and the "pipe" end goes on the top end of the feed pipe. You can od course join flexy tap connectors together in series to make any length.

Chris. You are correct, the cold feed is connected directly to the Neataheat and it is installed in the corner of a room so access impossible.

Since the cold feed is connected directly to the boiler I cannot see the difference between carefully applying mains to either the vent or to the top end of the feed pipe.

 

[cowboyplumber]

If you don't wish to listen to advice, why ask for it?

 

[felix]

Assuming that the blockage is at the bottom of the feed pipe, applying mains to this pipe will pressurize only a length of copper pipe. No problem there. If you apply mains to the vent you are pressurizing the boiler and all your radiators. They might hold but it's not something I'd like to try.

I've had some success in the past unblocking pipes with a simple bicycle pump. Simply jam the pump against the open end of the feed pipe and push. A tap washer interposed between the two will help.

 

[HO1]

If you don't wish to listen to advice, why ask for it?

Ok read the piece from Chris again and I understand it all now. Will give it a try.

 

[HO1]

Assuming that the blockage is at the bottom of the feed pipe, applying mains to this pipe will pressurize only a length of copper pipe. No problem there. If you apply mains to the vent you are pressurizing the boiler and all your radiators. They might hold but it's not something I'd like to try.

I've had some success in the past unblocking pipes with a simple bicycle pump. Simply jam the pump against the open end of the feed pipe and push. A tap washer interposed between the two will help.

Thanks for the suggestion.

I tried applying the water mains to the feed pipe but no success. So its a pump now.

 

[brumylad]

why not pour some system restorer down to see if that will loosen thing up a bit.

 

[felix]

So you couldn't get mains water down the feed pipe? That's one serious blockage. Just before you do anything more extreme, look for a valve in the feed pipe. I know this sounds stupid and you've probably thought of it already, in which case please accept my apologies.

If pressure won't clear it my next choice would be suction. Put a decent length of hose on the end of the feed pipe and get sucking! You never know your luck.

 

[HO1]

So you couldn't get mains water down the feed pipe? That's one serious blockage. Just before you do anything more extreme, look for a valve in the feed pipe. I know this sounds stupid and you've probably thought of it already, in which case please accept my apologies.

If pressure won't clear it my next choice would be suction. Put a decent length of hose on the end of the feed pipe and get sucking! You never know your luck.

I have had a look the whole length of the feed pipe and there is nothing, it is a direct connection down to the boiler. The Pump method did not work. So suction now.

 

[kevplumb]

the blockage is prob where the feed joins the boiler
if you can drain the head tank and cut a peice out
have a bucket handy it will be full of water

you could try pouring a acid cleanser in the pipe

after getting a small tube in and getting the water out first

have had to resort to it b4

 

[HO1]

Definitely blocked/scaled up at the entry to the boiler. Will try the restorer/cleaser method. Is Fernox Super Concentrate Restorer the best one to try?

 

[croydoncorgi]

To sum up....
Your whole system is currently completely empty apart from the cold feed from F&E to boiler and you cannot refill it.

Key issue is whether a cold solution of cleanser such as DS40 run down the cold feed will even begin to shift the blockage. I doubt whether 'System Restorer' would have any impact at all. (Most cleansers / descalers work best at 50 degrees or so.) If you can get the water out of the pipe so that concentrated cleanser hits the blockage, it MIGHT work after a while.

What's the closest point to the blockage you can cut into the cold feed pipe? Is there any possibility of getting something physical (such as a thin drain snake) into the blocked bit, and being able to move it up and down so as to hit the blockage quite hard? That close to the boiler, the material (probably brown oxide mixed with a bit of limescale to cement it together!) will be well caked-on.

Maybe the boiler's trying to tell you it's old and knackered, and wants only a decent burial.