Boiler has no isolation valves

[dominoman]

I am thinking of attempting a mains flush of my open vented central heating, as decsrived in the useful thread here: //www.diynot.com/forums/viewtopic.php?p=253454

However I have a few questions I am hoping someone can help with.

- My boiler doesnt seem to have any isolation valves, either inside it, or in the flow and return pipes leading to it. Is that normal? I guess this is the first thing I'd have to do so I avoid pumping crud through the boiler?

- I need to isolate the F&E tank. Where would the venting pipe from the boiler come from? Would it be the top of the hot water cylinder? (I can't see in the attic as the tank is hidden from view)

- I need to add a drain off point to the existing pipework in the cellar. What's the best way to do that? I can't find a simple drain off valve that fits in line with the existing pipe

Many thanks for any help. I hope my questions make sense.

 

[hanns21]

Flushing a open vent system with mains is a pain in the ass. And if your not sure what your doing the simplest thing you can do is take each radiator off one by one to outside and flush a hose through one of the ends of the rad. Should get your rads nice and warm again

 

[Bunnyman]

DONOT PUT ISO VALVES ON AN OPEN VENT BOILER VERY DANGEROUS,!
they don't have them for a reason u will be creating a bomb! They are ok on Combi etc as they have an in built pressure relief valve

 

[dominoman]

OK. Thanks. I didn't know about the isolation valves on an open vent boiler.

If I don't fit them won't all the sludge just pass through the boiler, whether I do a DIY mains flush or get a pro in to do a Powerflush?

So my options (heavily sludged system) are:

1. Mains flush (lots of hassle?)
2. Radiators off the wall (even more hassle?)
3. Powerflush (best, but expensive?)

What would you recommend? I am a fairly-competent DIYer and have done some basic plumbing before. Changing valves, fitted Magnaclean etc

 

[Dean744PiN5]

why not fit a magnetic filter to the boiler, if going to the trouble of flushing.

 

[dominoman]

why not fit a magnetic filter to the boiler, if going to the trouble of flushing.

Yes, I have just done that. I was hoping that a magnetic filter (I used a Fernox TF1) plus the anti sludge chemicals would do the job. But my radiators are almost totally cold except a little area at the top. The system is so full of gunk that I think I need to be more drastic.

 

[jackthom]

Depends on location and how good your access is but if possible I would get the main 22m flow (just after 3 port valve) disconnected and the same with the return just before the boiler. Then you should be able to mains flush the system/radiators with no connections to the boiler or vents, (mains water to return and drain from the flow for a backflush).

When a radiator has been hot at the top for a while, is hot water coming out of that radiator return or cold water? ie is it sludge in the radiator or poor circulation (or likely both).

 

[dominoman]

Depends on location and how good your access is but if possible I would get the main 22m flow (just after 3 port valve) disconnected and the same with the return just before the boiler. Then you should be able to mains flush the system/radiators with no connections to the boiler or vents, (mains water to return and drain from the flow for a backflush).

So if I do it this way I wouldn't need to do anything to block off the vents to/from the F&E tank?

I have a drain point on the return by the boiler already (where I fitted the magnetic filter) so I could use that to drain.

Then I simply attach a mains pipe after the 3 port valve? Is that the valve that has AB - A- B on it? So I attach cut the pipe after the A and fix a mains hose to the pipe (in the direction leading away from the 3 way diverter).

Just want to check I have understood?

I like the idea of doing it myself. Partly just for the satisfaction of seeing the gunk emerge.

 

[jackthom]

Yes that should work going into the pipe connected to the A port.
It may be useful to reverse flush it in the opposite direction as well, with the mains water going into the return pipe this time.

The vents should be between the boiler and the pump both of which will be isolated from the flush. Go slow at first until you are happy thet nothing is escaping where it shouldn't.

Then try a bit more pressure with only one radiators valves fully open at a time.

 

[kbdiy]

Given your description of the system I will still opt for removing each rad and flushing outside with a hose first. Trying to force it round with mains pressure is all well and good if you can get a good flow going but if it is as badly sludged as it sounds you might waste a lot of time and not get a decent result.

You will also need to gain access to the F&E tank, not just to isolate but also to clean it out before refilling.

In my view (and I did this last year on my system, so have some recent experience) getting rid of the bulk of sludge from the rads first gives a much better chance of cleaning the system thoroughly.

I am slightly concerned by a comment in your first post about the vent coming off the top of the hot water cylinder. That vent has nothing to do with the heating circuit so I would suggest you get a better understanding of the system pipework before you do any damage.

 

[dominoman]

Great! Thanks for the advice. I'll give that a go.

One more question. What would be the best way to connect a hosepipe to the pipe coming out of the 3 way valve?

I've looked online but can't find a suitable fitting that turns a 22mm pipe into a hosepipe connector end.

I'm looking for something like this, but with a compression fitting.

Untitled

• dominoman
• 14 Nov 2014
• 1

Is there any other (better) way to connect my hose to that 22mm pipe temporarily?

 

[dominoman]

Given your description of the system I will still opt for removing each rad and flushing outside with a hose first. Trying to force it round with mains pressure is all well and good if you can get a good flow going but if it is as badly sludged as it sounds you might waste a lot of time and not get a decent result.

You will also need to gain access to the F&E tank, not just to isolate but also to clean it out before refilling.

In my view (and I did this last year on my system, so have some recent experience) getting rid of the bulk of sludge from the rads first gives a much better chance of cleaning the system thoroughly.

I am slightly concerned by a comment in your first post about the vent coming off the top of the hot water cylinder. That vent has nothing to do with the heating circuit so I would suggest you get a better understanding of the system pipework before you do any damage.

Thanks for the help. My answer above was in reply to the previous post.

I was going to try this mains flush first only as it does seem a bit easier than removing every radiator. My radiators are very old cast iron and weigh a ton.

My F&E tank is almost totally inaccessible unfortunately. I can get to the feed pipe but can't get to the top of the tank to see in or to clean it.

 

[jackthom]

i'm sure someone here will have a better way of connecting up the hose but last time I just used what I had available ie warmed the hose end so it went over a short 15mm pipe, held with a jubilee clip. Then a 22/15 compression fitting.

It wasn't inside the main house area so had it slipped off it wouldn't be a disaster.