Green/Yellow colour from radiator

MEJBelloz

Hello,


DIY novice here, as well as a first time home-owner.


I've recently had a brand new boiler put in to a house that is around 70 years old. Originally the boiler after fitting, the pressure was dropping over a few weeks and leaking, so engineer come out and identified a leak from the cold water pipe and fixed. I re-pressured the boiler back to 1.5 bar.


Recently I've noticed the boiler is down to just over 1-bar when off (I know this is still within the expected zone), and its closer to 1.5 when the heating is on. I wasn't expecting the pressure to drop so close to 1-bar so soon after re-pressuring (3-4 weeks).


I've checked the boiler, no obvious leaks on the joins, and I've checked the radiators with no obvious leaks either. Due to the small rate of pressure drop, I assumed I might have a very small leak, so I placed some tissue around the pipes on all the radiators. After 6 hours of the heating being on, all the radiator tissues seemed dry, but one upstairs one had some very small green/yellowish coloring on the tissue (very small 1cm size).


I can't tell if it is just gunk on the pipe (maybe the previous owner put sealer on the pipe), or whether it is a sign there is some water coming out whilst the heating it on? It seems he has also painted all the pipes going to the radiators, except the pipes on the radiator themselves.



What do you guys think? Would the pressure drop by 0.3 bar in 3-4 weeks? Could the stains on tissue possibly due to a small join leak on the radiator? I was wondering the green could be the cleaner the engineer used when putting the boiler in.



I don't want to assume its a leak under the floorboards yet (as no signs), but also realize that boiler pressure dropping, especially slow, can still be a small leak I can address myself.


Thanks in advance guys!

MEJBelloz

BUMP - can someone help... the boiler pressure is now just below one when off (I'll top it up, but clearly losing water somewhere).

I put some more tissue around the pipe for the one radiator and was definitely stained brown and green (various spots) when I took it off a couple days later... so would this be the issue? It feels sticky to touch the pipe as well, but not sure if it's because water has been heating on there, or stuff the previous owner put on the pipes.

Any help would be appreciated... thanks!!!

FreeBear

Use a spot of washing up liquid & water to clean the sticky gunk off the pipe(s). If you have an adjustable spanner, go round all the radiators and nip up the nuts on each pipe. If they do need tightening, then it will only be a sixteenth of a turn at most.

If the pressure is still dropping, it could be down to a leak in the expansion vessel. Unlikely to be a pipe as you would soon notice a stain appearing on a wall or ceiling.

shockrisk

It'd be worth letting the heating system go cold then seeing if you notice any small leaks, the system will still be under pressure and joints have a tendency to seal themselves when warmed up or dry out faster than the leak is occurring. If this doesn't yield any useful results then the problem may be elsewhere. I'm assuming you have an unvented heating system? You'd need to arrange for someone who is competent in the installation and servicing of such a system to further diagnose the issue. These types of system are required to be setup in a specific way and if not done correctly can lead to the exact situation that you are experiencing at the moment.

southcoastrgi

A leak on the cold pipe into your boiler will have nothing to do with your pressure gauge dropping

howlsatthemoon

If you suspect a small leak in the system try some leak sealer. Google "central heating leak sealer" and see what different products are available.

Rodders53

Don't use leak sealer except as a very last resort.

I agree that clean off the 'gunk' and have a check of nut tightness. Gunk might have been a smear of plumbers paste of one variety or another around the olive of the compression joint. https://www.emergencyplumber.uk.com/plumbing/best-plumbing-paste/

There should be no need for such thing on good quality compression joints and pipework though.

Check if there are any automatic air vents in the system on the heating pipework in the boiler in some cases. These will let air out that is naturally dissolved in any water used to fill the system but released when heated up... and that air may also collect in the tops of radiators etc.,. and then released manually? Have you been 'bleeding' the rads? That air can account for such pressure loss.

On a 'brand new system' I'd expect this to take quite a few weeks to happen and for pressure to become steadier.

Old rads may also leak slightly from the TRVs and lockshield valve spindle areas. The slight water loss is often evaporated off, but may be another cause of a slow pressure loss. Examination when cold is best.