Finding leak in copper pipes in concrete

[jenningsp]

Can anybody give their experience of finding a leak in central heating feed pipes buried in concrete using thermal or similar detection systems. Leak seems to be worse when system is hot and total loss is about cup full every two or three days.
If pipes need to be bypassed any views about putting a new surface channel in concrete rather than dropping down from floor above. Total length of channel required would be approx 7 metres including a couple of tees to different radiators.
Any feedback gratefully received.

 

[Slugbabydotcom]

Thermal detection system consists of a laser thermometer that they sell in Maplins for about £25 if you catch em right and £50 if you catch em wrong. Trace the pipes with the heating on. Its odds on that the leak will be at a joint in the pipework and you may notice a damp patch. Look for rooms where the windows mysteriously steam up or that feel damp when you walk into them. Check areas where wood floors meet concrete and damp corners or joints in the concrete floor.
Can you remember when the problem started ? Was it just after you had a kitchen fitted or some new skirting or paneling perhaps ?
In my experience unprotected joints in concrete can last a very long time but its only when they get damp from another source that the joints are attacked by the chemicals in the concrete causing a leak. Leaks from thermal expansion and contraction I find to be a lot rarer.

The 'drop' method is my preferred way of putting the job right but if you insist on going through the floor I suggest that you find a proprietary ducting method

 

[Agile]

All those I have found so far have been at the elbow under a feed to a rad.

Its best to have the system cold and over pressurise to enhance the leak rate.

Then putting a sheet of glass over the concrete floor will often cause condensation on the underside close to a leak.

A thermal imaging camera is very good but not available at a sensible price. I have never had much success with an IR thermometer.

A damp meter is also very good, in fact, probably the best method! You dont have to have a dedicated one as a good multimeter with a 20 Meg range and sharp probes is almost as good.

Tony

 

[fizzput]

I managed to detect a leak recently because i could hear it, very faintly anyway, as a hissing sound from the raidator in that room....still had to dig up the floor and trace the pipes, first elbow i came too had 2/3 mm of pipe inserted and soldered.....

Apperently the guy who installed it was a really quick worker

 

[Agile]

I should also have mentioned that a big leak on a joint will be hearable using a mechanical stethoscope on the rad tail if its on the elbow underneath.

However if its only a smaller weep then it will not make enough sound.

I also have an ultrasonic sound meter which is good for gas leaks but not enough HF noise is made by a water leak unless its from very high pressure like 3 Bar +

Tony

 

[spacethegas]

ultrasonic sound meter which is good for gas leaks

not taking the mick.

please explain how this may be used, as i am unfamiliar with this device & its use in pinpointing gas leaks ?

seekers & devices utilizing an ion flame for external use (i might have got something wrong there , but i know what i mean), i am familiar with.

 

[Agile]

When gas escapes under pressure from a small orifice it makes what we hear as a hissing.

Thats effectively "white" noise but we only hear the part of the sound within our hearing range. A young person can hear up to about 16 kHz but as aging occurs the HF response drops off quite considerably and few people over 55 probably can hear over 10 kHz. At 70 its probably down to 5 kHz which is why old people have to be talked to slowly and clearly!

Age related high frequency hearing loss is called presbycusis. This starts at about age 20.

I used to be able to hear bat's doplar sonar when I was at school!

Amusingly school kids can now download high frequency ring tones which their parents and teachers are unable to hear !!!

The ultrasonic meter has a microphone and mixes the audio spectrum it hears with a local oscilator at perhaps 32 kHz and allows you to listen in to the spectrum between 16 kHz and 32 kHz.

The spectrum of light gases escaping produces more "white noise" above 15 kHz so the meter enables the sound to be detected which would not be heard by the naked ear!

Tony

 

[spacethegas]

sorry bud, i cant see that as any assistance in finding the location of a gas escape.

i know that my hearing frequency range has reduced over the years. there are sites on the web where this can be tested.

i have in fact been tested for it in the past due to medical problems.

i cannot see any relevance in regard to gas leak location.

the best thing to take in to account in regard to a reported gas leak is.............

if a woman can smell it the chances are, there is a leak.

tell me if i'm wrong.

 

[Onetap]

I also have an ultrasonic sound meter which is good for gas leaks but not enough HF noise is made by a water leak unless its from very high pressure like 3 Bar +

Tony,

What make is your ultrasonic leak detector? I need to get one.

Just to confirm what you have said above, they are very useful for finding leaks from compressed air, refrigerant and steam systems. A gas/steam/ air leak generates a loud, but inaudible (if you know what I mean) ultrasonic noise when it escapes through a small orifice.

I has access to one in a previous job. There was a mechanical plantroom with a lot of big, noisy, old fans; it was so loud you were meant to wear ear defenders in there. The heating and chilled water 3-port valves had pneumatic actuators. I checked the pneumatic system with the ultrasonic detector; despite the background noise, with the headphones on, you could clearly hear an air leak from a 15psi 1/2" compressed air pipe, which was about 4m above floor level. It had been leaking since installation, some 25 years earlier. The leak was fixed, the compressors' 'Hours Run' readings immediately halved.

High-frequency, ultrasonic sound is easiest to attenuate, so you may not hear a leak if it is out of sight; the sound loses a lot of it's energy when it is reflected off solid surfaces.That is also why, when some moron has a party at 2 am, the main noise you hear is the bass drum boom, boom booming. The high frequency noises don't travel as far as the lower frequencies.

With heating you'd drain it and put compressed air into the system, at a pressure below the working pressure. With gas you'd have to disconnect from the meter to apply air pressure. I've never tried it on mains pressure gas; I've found a gas sniffer to be less hassle.

 

[Agile]

That is also why, when some moron has a party at 2 am, the main noise you hear is the bass drum boom, boom booming. The high frequency noises don't travel as far as the lower frequencies.

The reason you can only hear the bass boom from the party at 2 am is because of your hearing loss from old age!

If you were young with an entended high end response you would be at the party instead of complaining about it!

My instrument is appropriately called an ICC Leakcheck it was supplied by RS.

It comes in a black case similar to the electric drill and thermometer cases which I opened first.

It operates on a centre frequency of 38 kHz and has a frequency response to -3 dB points of 27 kHz to 48 kHz. It has a speaker and a headphone socket and an LCB bargraph meter.

Tony

 

[Onetap]

The reason you can only hear the bass boom from the party at 2 am is because of your hearing loss from old age!

If you were young with an entended high end response you would be at the party instead of complaining about it!

Actually very true, but still funny.
I lost much of my high frequency hearing to one very big boom near my right ear about 25 years ago but the effects didn't show up until 20 years afterwards.
And my old age.

 

[Agile]

If you were young with an entended high end response you would be at the party instead of complaining about it!

Some might say that I am not so young but I am still going on a disco boat on the Thames on saturday night and to an (ex) soldier's wedding on Sunday. Must remember to find out the RP.

I did once expect to teach the soldier plumbing, but he ripped me off with the wedding pictures he took at a wedding a few months ago. He showed me two the same and I asked how much I owed him. He replied £10 so I gave him £10. He then said "EACH". That ended all thoughts I had of training him! Its no wonder he did not want to do the disco at that wedding for £200, he must have made £1000 from the pictures instead.

When he was a soldier a year ago, he was no stronger at arm wrestling than me but he did have more stamina. He might have just been being "polite" though!

His Mother in law needs three chairs to sit on! His wife used to need two but has lost a lot of weight lately.

Tony

 

[Onetap]

That ended all thoughts I had of training him!

Tony

A bad move on his part.

One other way of finding a leak in a concrete floor, if it's a kitchen or bathroom floor, is to get a mop and give the floor a good clean. The water remaining on the floor will evaporate over the line of the pipes first, a leak will sometimes show up as a circle on the line of the pipe.

Copper heating pipes buried in concrete are bad practice; there will be a huge heat loss from them into the earth, unless it's a part of an underfloor heating system. The long-term plan should be to cut them out or by-pass them.

 

[spacethegas]

well i've learnt something today.

the use of the meter & Onetap's last post re mopping the floor.

good idea.