CH draining - this OK?

[Hallsy]

Yep, I'm slowly learning!! If I hadn't finsihed in time I would;ve just left the hot water off until tomorrow, but the missus would've moaned - tough

This is the trouble with shifts, on a late shift you always have to be mindful that whatever you're doing you need to be ready to go to work on time

 

[Hallsy]

Used a 3/4" - 1/2" socket with a 1/2" hose connector on the end and drained from a rad valve, all OK

Did what I wanted to do, just untied the ball cock to refill, header tank is full, but nothing at any rads

Opened bleeders, nothing.

Opened the rad valve that I had the hose on again, nothing.

Airlock? Blockage?

Should I try running the pump to see if that makes any difference?

 

[JohnD]

perhaps you have a sediment blockage in the feed pipe. It's not unusual. Especially if you got black water and sediment out when you drained.

As a temporary expedient, you could put the hose, from your drain point, on a tap, and let the water flow in "backwards" from the bottom up. This method of filling can also be used if you suffer from airlocks.

To identify if there is a blockage:

1) when you drained the system yesterday, did the F&E tank empty?

2) When you refill from the bottom, does water and air flow up into the F&E tank through the connector at the bottom? Or does it come out of the vent pipe curved over the top?

If you do have a sediment blockage, it is almost invariably at the tee where the Feed pipe joins on to the main circulation pipes (usually close to the pump). You can detect the presence of a blockage in this copper pipe with a magnet, which is attracted to the black sediment lump inside.

p.s. don't run the pump if it is dry

p.p.s If you fill it from a hot tap, or a bathroom tap (which comes from a loft tank) it will not overflow (much) like it would if you connect to the mains, as the max water level will be the top of the cold water tank in the loft.

 

[Hallsy]

Cheers John, yeah should've thought about pump running dry.

When I drained system this morning the header tank drained down to about 1cm left inbottom. Water was fairly black out of rads as expected. Water in header tank is orange? Also someone has left a netted bag in there with some sort of chemical I guess in there.

Anyway, I'll try what you suggest.

So from same rad I drained from if I connect other end of hose to a tap/water supply then watch from header tank? How will I know when it's full, once header tank starts to overflow?

Are you suggetsing I don't use mains water then? I have easy access to a downstairs outside hose that I could backfill it with, but this is mains pressure.

 

[JohnD]

when water comes out of the overflow from your F&E, it has reached the top. When you bleed the rads it will pull more water down, but if the problem was an airlock, it will draw this from the F&E (if there is a blockage, it won't be able to, and you'll have to add more through the hose)

If you use mains supply, the pressure will be higher, so it will come out of the overflow quite strongly. It might even overwhelm the overflow and come over the top of the F&E. However if you refill it from the hot tap, the pressure will be almost gone by the time the F&E is full, because it will be about the same height as the supply tank. This will reduce the overflow.

If you refill it from the mains tap, it might be best to have someone up in the loft watching the F&E fill so that they can shout at you when to stop filling.

Orange water is recent rust. So you need to do (at least) a chemical clean and refill with inhibitor when you've finished your replumbing.

 

[Hallsy]

Right, connected downstairs rad valve to hose pipe and turned water on, just low pressure to start with.

Started getting air bubbles at header tank, then lots of air bubbles, then after a while it stopped and water started coming up over the vent.

I have just turned the hose off and left it draining again to see if the header tank drains, which will hopefully show that the blockage/airlock has gone.

Incidentally, I have a radiator removed both upstairs & downstairs, but this shouldn't make too much difference to draining/filling should it,as all the flows/returns are connected to each other?

 

[Hallsy]

It drained OK, although very slowly.

I can see what the problem is now, the flow fill pipe is almost totally blocked with scale

Going to have to try chiseling it away. Would cut and remake the pipe at back of header tank but access is very awkward/limited.

This bag of whatever it is hanging in the tank, should I chuck it?

After seeing this I'm definately going to clean and then add inhibitor afterwards.

Any recommended brands, tips, etc? Do I risk blocking up the heat exchanger, pump, etc by using a cleaning product on an old and what looks to be pooryly maintained system?

 

[JohnD]

Sentinel and Fernox are good brands of CH chemicals and are widely available.

I've heard you need to leave the Sentinel cleaner in for a few weeks to clean away all the stuff.

There is a Fernox one called DS40 which is very strong, maybe hold off on that for now if you think the system is in poor condition. I am just householder, not a heating engineer but have done these things in my own house. Although people sometimes say the cleaners have caused leaks, what they really do is to remove scale and sediment that is blocking existing holes.

Is your blockage hard black sediment? If so, there is a device you can buy that will capture any of it that is circulating loose in the water with a magnet. This prevents future build-up. If you fit one on the pipes leading to the boiler, it will trap loose sediment that might otherwise collect there. The Magnaclean is a good one, and will cost you in the region of £100.

If you can flush away much loose stuff, it will allow your cleaning chemicals to get to work afterwards on the remaining hard residue.

If you have a blockage of scale from hard water, you probably have a leak. Otherwise, the same water just recirculates, and does not add further limescale.

If you have had sediment circulating for a long time, the pump may well be worn, but it is a replacable part if it fails.

Have a go at taking out the F&E and renewing the pipe, it will probably save time in the long run.

It sounds like you will be doing a lot of flushing and draining, so consider fitting a full-bore drain off tap. It will make draining a positive joy in future and will flush out more grime.

 

[Hallsy]

It is white scale that has blocked the flow fill pipe.

Howver I'm wondering if it's the bag of white stuff that has caused this as the stuff it appears to be filled with is floating about everywhere.

The rads had black water in as usual, but it wasn't thick.

I'll see how I get on at unblocking it from the front, if no good then I'll have to try to remove the header tank as you say

Oh, and by leak, where do you mean? Within the CH system? As far as I know I have none, I have no damp patches anywhere.

 

[JohnD]

"yet"

Some leaks are small enough that the water evaporates away, though they usually leave a brown or black stain from the dirty water.

A leak under the floor is usually not noticed.

A dripping ball-valve will keep topping up the water and addding more hardness (and air) but will also leave a "tide mark" at the level of the overflow.