Gas leaks

[Guest Bill H]

I haven't got one but a reader in the December MMM issue did have. I use several types of dangerous gasses daily. A very simple test for leaks when the system is pressurised is half a cup of very soapy water and a 1" paint brush. (Escaping gas also means it's costing you money)

[Guest Derek Uzzell]

I accept that the technique you've suggested should reveal an individual gas leak, Bill, but it won't confirm the integrity of a motorhome's complete gas system. Even if you went round every joint you could find with a soapy paintbrush you still wouldn't be testing for possible leaks from unreachable joints, gas-taps, heater solenoids, etc. Better to install a purpose-made leak tester (available from Alde), or replace an ordinary regulator with one with a pressure gauge (as offered by Gaslow or Truma), that can be used to check the gas system conveniently and regularly. It's a shame that the UK standardisation of the bulkhead-mounted 30mbar regulator for leisure vehicles didn't include an obligatory pressure gauge, especially when one realises that the extra cost is so small (a Truma 30mbar 'fixed' regulator with pressure gauge costs about £4 more than one without).

[Guest Bill H]

Yes 'D' I accept your comments. A M/H or sealed box is very different to an open workshop. I assume with a pressure gauge, if it registers a loss when the system is not in use then there's obviously a leak somewhere, but this would require constant monitoring. Can you describe the leak tester. Is it mobile or attached somewhere. or as someone recently mentioned, an off the shelf attachment for the interior of the unit. I wonder if there are instruction on where to attach it? High in the vehicle is not much good when the gas in use is heavier than air. In the gas locker that has access to open air would also be useless. Of all the hazards in life escaping gas is one of the most serious.

[Guest Brian Kirby]

Bill The gauges aren't really all that difficult to use. You connect your gas bottle/s and purge all the air from your system unti all appliances light normally. Then turn off the gas at every available point, including the main gas cock, leaving your bottle/s connected and "on". The gauge will now regsiter the pressure on the first leg of your saysem. You then turn off the gas at the bottle and leave it all alone for a while (they recommend about 20 minutes if I remember, but I always leave it a couple of hours), then return to see if the pressure has dropped. If it has, there is a leak and you check all the connections between the bottle/s and the main gas cock. Remedy as becessary and then turn on the feed to just one appliance. Re-pressurise as necessary, go away again, returning as above to check pressure and remedy leaks - and so on, doing each leg of your system individually, shutting off all other legs, until you've done them all. As a finale, I then turn the gas on to all the appliances, fire up each in turn, turn them all off again, and then, leaving all the feed cocks open, turn off at the bottle and leave it all over night. If the pressure had dropped more than a bit by the next morning I repeat, leaving each leg a bit longer than before until I find the leak I've missed. I can't vouch for the sensitivity of the detectors but, with a properly installed system, with all the required gas drops installed and clear of obstruction, I'd be surprised if they are more sensitive to leaks than the above method. The drops should clear any leakage before it gets to the detector. After all, the sysetm pressure beyond the regulator isn't that high, and the volume of gas in motorhome tubing, even between the bottle and the most remote appliance, is really quite small, so any drop on the gauge really represents a very tiny loss of volume indeed. My point is not that such small leaks are unimportant, but just that this test responds to very small volume losses, so is a highly sensitive indicator. Incidentally, you can do the same with the auto changeover valves as well. As above, but turn on one bottle only, set the valve to use that bottle, leave the other bottle off and proceed as above. If there is leakage, the auto valve will "see" this as the supply bottle running out and seek to change to the other, so changing colour. You can then turn the first bottle off, open the second, set the supply to that bottle and test just the connections on the "tail" to the second bottle. It does all take a while to complete, but you only have to do it, say, once per year. The rest of the time the system tests itself every time you drive: you do turn off at the bottle/s first, don't you? Any pressure loss on your system between departure and arrival indicates a leak. Easy, innit? Regards Brian

[Guest Neal]

Bill H From trade training of over 30 years it has always been said that the "chemicals" in soapy water will rot the jointing compound or sealant used, resulting in gas leaks where there were once none! Everyone knows, and usually says, that soapy water is the way to test for leaks but, watch any professional completing a test and you will NEVER see soapy water used. Trust me, it can be dangerous. DO NOT DO IT! Regards Neal

[Guest Bill H]

Thanks all round. The gasses I get involved with do not have a compound material in the joints. They are always metal to metal. The procedure layed out by Brian sounds logical but HOW (?) does one find a small leak in a difficult place. Is there an detector that incorporates a probe?

[Guest Neal]

Bill H The answer is yes. Most testers have probes with the sensor on.

[Guest Derek Uzzell]

Bill: I'll describe the Alde, Truma and Gaslow products separately. The Alde leak detector is fitted in the low-pressure side of the motorhome's gas system. Depending on the type of system, it will go between the low-pressure flexible hose and the fixed 'tubing', or between the bulkhead-mounted regulator and the fixed tubing. The detector carries a test button that, when pressed, indicates the presence of a gas leak by bubbles forming in a small glycol filled reservoir. Truma offer a 30mbar bulkhead-mounted regulator fitted with a clockface-type gauge providing a numeric read-out of the gas pressure within the system. The gauge also has a red 'tell tale' hand that can be moved to record that pressure and thus make it apparent when a pressure change occurs. Gaslow market a variety of dial-type products that they refer to as "Low Level Indicators". These are integrated into Gaslow regulators or may be purchased as add-on adapters. Rather than having a numeric display these have a 'window' behind which is a colour-coded rotating disc that is intended to warn users when their gas reserves are running low (though I have to say I've never found it particularly confidence-inspiring for that purpose). However, they are valuable for leak detection. Gaslow's instructions are: Ensure all gas appliances are turned OFF. Turn ON the gas at the cylinder, the window will show GREEN. Turn OFF the gas. Watch the gauge. If the RED sector appears in the window within the specified time, there is a leak. Should you see RED, check your system and locate the gas leak (From what I recall, the recommended "specified time" is 10 to 15 minutes.) If a leak were detected, the progressive testing method Brian has described using a gauge should pin its general location down. As he says, with a leak-free system, there should be no movement on the gauge for a long period after the gas container has been turned off. However, leak checking can't guarantee that your gas system won't suddenly develop a fault - that's when a gas detector could prevent an accident. You would need to install it close to the floor and, if your 'van has (say) a gas-stove at the back and a gas-heater at the front, fitting more than one detector would make sense. Back in the summer I was advised by a UK dealer that gas 'drops' were now being omitted from the living-area in many UK motorcaravans. He said this was due to EU harmonisation, as Continental motorhomes only required gas-drops in the gas locker itself. (Certainly my Hobby has no drop-vents except in the gas locker.) I've always been sceptical of the effectiveness of the gas-drops I've seen. Although LPG is heavier than air, it's not that much heavier. Cutting a small hole in a leisure-vehicle's floor somewhere near a gas appliance and expecting leaking LPG to disappear through it like water down a bath plug-hole seems to assume active co-operation on the part of the gas or an extraordinary degree of optimism. If you want a hand-held leak-tester, you could try a Focus DIY store as I've seen them there at about half the price of identical products advertised in leisure magazines.