Underground heating pipework and flushing.

[Bogart]

Right have decided to have a good go at my heating system so I have basically 2 questions.

1. I have an old oil boiler situated some 25m away from the house. It leaves the boiler in 28mm copper changes to 35mm copper in the boiler house , exits the boiler house and goes underground and just before it enters the house changes to 2in
steel pipe. This winds it way up to the airing cupboard , pump and controls live here where it then goes directly to 28mm copper. My concern is the copper pipe passing under the lawn from boiler house to actual house. Have excavated some ground to see what was there and the copper pipe is buried around 400mm deep. It has insulation on it but this is so water logged as to be useless. This is evident if say there is snow on the lawn as there is a green strip visible across it. Now I have considered replacing this with twin pre insulated pipe. Now first question is there an alternative insulation I could fit over the existing buried 35mm copper pipe? I do not want to fit some insulation that in a couple of years is a bad as it is now.

2. Now next question is regarding flushing. The property has, or more aptly until the weekend had, 23 radiators. These varied from old to ancient. They have now been removed so I am left now with lots of 15mm pipework with no rads connected. The pipeworks are capped off with the old lockshield valves. So I am now thinking maybe a good time to flush the system. I could rig a bit of flexible up and flush each radiator position pipework in turn. Or should I wait until I fit new rads and then do it.
Seems to me better to do it now so as to not introduce muck into new rads. I have Fernox TF1 fitted in the boiler house.
I was thinking of getting an Adey Magnacleanse to do this. As I am not on a direct sewer, I have a treatment plant so cannot dump waste fluids in there. I have a large soakaway also but only want to dump as little cleaning fluid as possible into it for obvious environmental reasons. Any suggestions as to the best way to proceed.?

Thanks

 

[Ric2013]

Bear in mind new radiators may have small quantities of swarf and oils (could damage any rubber in the system) from the manufacturing process in them so won't be entirely clean. On a modern system, I'd suggest flushing after installing new radiators.

As far as the Adey Magnacleanse is concerned, I own one, but don't rate it for flushing unless used in conjuction with a powerflush machine. Perhaps Adey's magical chemical makes it work (I remain sceptical), but chemicals are what you say you want to avoid in this instance.

Realistically, if this is to be a DIY job and water seems to flow around your system without obstruction, you could do worse than use the mains to flush through your existing pipework before new radiators are fitted (flush the boiler separately if you are concerned about shifting dirt into it) and then filling and draining a few times. As old boilers are much more tolerant of 'poor' water quality, you may well find that the old method: a cold fill, circulate and drain, then refill, heat the system, circulate and drain and then finally refill (with inhibitor?) will then be sufficient once you have installed the new radiators.

 

[Bogart]

Good suggestion as before rad removals they all seemed to heat up fine. Just using water will obviously mean I can send to the treatment plant. The currently fitted TF1 does catch some magnetite. The previous owners I think never bothered to treat the water hence I am getting rid of their magnatite. I suppose I could flush a few times and see if the TF1 still catches anything. I will need to do new quite a few soldered joints so will be introducing a fair bit of flux into the setup unfortunately. I have a Rothenberger Superfire 2 would it be sensible to braze and not solder. Never ever brazed yet.