Propane leakdown

[ajriding]

I put a pressure gauge inline between the tank and regulator for the first time ever.
After I shut the gas off the pressure on the gauge will drop overnight from green (pressurized) to the red (meaning low low pressure).
Should the pressure on the high side remain high for days/weeks or is it normal for that to drop? Im not sure if the regulator is venting it or if I have a leak after the regulator.
Nothing bubbles, but there is one fitting I cannot get to.
I used Nylog on every fitting.
3/8 copper and flare fittings.
There is only a space heater (has solenoid valve) and a stove.
I cannot detect any odor.

[ajriding]

I put a new hose from the tank to the regulator. Soaped it up and no bubbles on the hose crimp, or the connection at the reg. No bubbles anywhere.
Everything is new except the furnace.
The Nylog means the flare fittings are not leaking too.
The only thing unknown is the furnace solenoid gas valve. No propane smell though.

So, the pressure dial still goes down in pressure within hours. Is this normal, again??

[time2roll]

dougrainer wrote:
There is no such thing as a completely sealed LP system. The system will leak down the LP in the system when the Tank is turned off over days/weeks.
YOU NEVER USE OR NEED TO USE ANY SEALANT ON A FLARE FITTING. NEVER!
If a flare leaks FIX the copper flare, do not attempt to use sealant. PIPE fittings, you use sealant/teflon tape. Doug

Thank you for this information. I have always wondered about the leakdown after storage.
I agree no sealant to be used on a flare.

[C_Schomer]

I have a an OLD Marshall reg that comes apart and I've made new viton internal parts to keep it working but a couple of weeks ago, I thought it was finished. I smelled mercaptan and I soaped it repeatedly and I couldn't see bubbles but when I rinsed it off and watched a little longer, I finally saw a TINY bubble in the water, on the bonnet of the low tank gauge. The bubble was too tiny to show through the soap. Water actually worked better than soap, that time. I checked the gauge diaphragm and all I had to do was tighten the bonnet nut a little tighter. Maybe I'll get another 20 years out of it. Craig

[ajriding]

Thanks all.

I think everyone is fine if someone does not want to use a sealant on their lines, copper flares should seal almost all of the time if done right, good luck.

The Nylog is not a thread sealant, though works great as a thread sealant, rather it is designed to seal more than that.
It looks and feels like snot, and it does not dry ever, and does not blow out. This is not a glue, but more of a gasket that remains tacky and liquid, but will restrain very high pressures.
Adding Nylog to a connection that does not require a sealant is harmless, and will ensure you have the best and most long lasting seal possible.

I have been able to re-use crush washers because of Nylog with no leaks.

On my current new copper piping the Nylog even held pressure with just a hand tightening of the flare nuts, something that could never ever happen without it.

I highly recommend using this product on your pipe fittings.

There are two types, Red and Blue. I use the Red for this application.

It is also "food safe" and used in the refrigeration industry on large units.

I do not work for or represent the brand, but just sharing good info.
I got mine on Ebay for about $9. thanks

[JimK-NY]

ajriding wrote:
So, it is not normal for the pressure to leak down overnight?
...

I think this is normal. I have not done a lot of experimenting but I know my regulator gauge goes from green to red within a day or two, perhaps even quicker. I have no idea where the propane goes but otherwise I have never had any indication of a leak.

[dougrainer]

ajriding wrote:
So, it is not normal for the pressure to leak down overnight?

This is not a red/green indicator as on a two-tank system, it is a dial, green range is full tank, as tank pressure lowers the dial moves into a red colored background (not unlike the red in your rpm tachometer).
The dial measures psi and shows this with a needle.
I should have explained this more clearly at first.

Nylog is the stuff. It is cheap insurance for sealing things. It is used in the refrigeration industry as gospel. Use it on all your propane fittings from now on. Teflon tapes are of the past now unless you need to lubricate the threads..

I did not use Nylog on the tank fitting, possible that is a leak? I will go bubble check that and nylong it and retest.

**also, this tank I have had sitting in garage for 6+ months so I do not suspect it is leaking when closed.
Temps change very little overnight here during summer, not enough to swing psi this much.

If this is not normal then I will assume it is the pigtail, which is the only used part in the system other than the heater.

I guess you are testing the fittings/pigtail between the Tank connection and the INPUT of the LP regulator? If so, either the Pigtail is leaking at the crimp or your gauge has an inherent leak. Pigtails can leak when they get older at the crimp ring that secures the rubber to the fittings. Doug

[dougrainer]

AND I STAND BY MY STATEMENT, YOU DO NOT USE ANY SEALANT ON A BRASS FLARE. FIX THE FLARE, DO NOT USE SEALANT. Doug

[dougrainer]

THIS is the sealant to use. This Rector Seal will seal up to 3500 psi.
Doug

https://www.lowes.com/pd/RectorSeal-No-5-Pipe-Thread-Sealant-Sealant/3134515?cm_mmc=shp-_-c-_-prd-_-...

[MEXICOWANDERER]

Old-Biscuit wrote:
RV Propane Leak Test.......

High Pressure Side (before Regulator)
Turn the main LP Gas Valve to the on position and listen for the initial PSST sound. After a second or two, the sound of flowing LP should stop.
Next step is to notice the green band in the clear regulator cap. Now turn the main LP gas valve off at the LP tank for
3 to 4 minutes.
Watch the green band in the clear regulator window, and it should stay green. If it turns red, (low gas indicator), this indicates a possible leak.

Low Pressure Side (after the Regulator)
Requires using a manometer connected to system.....stove top burner at manifold can be used
Valve in Propane Supply....verify system is 11"WC
Valve out Propane Supply...then slowly open burner knob and drop system pressure to 8"WC then close burner knob
Monitor pressure for 15 minutes....no change in system pressure then system is GOOD

System pressure drops....how fast will indicate size of leak
But only 15 minutes is required for leak down test on low pressure side
And only 3-4 minutes on high pressure side

Doubt you have a leak....indicator green/red is NOT a accurate means of testing

This is why I have a shutoff c0ck valve behind every propane appliance. My Manchester motor fuel 83 gallon tank has a high flow block off that stops the flow 100% and stays 100% shut off.

[ajriding]

So, it is not normal for the pressure to leak down overnight?

This is not a red/green indicator as on a two-tank system, it is a dial, green range is full tank, as tank pressure lowers the dial moves into a red colored background (not unlike the red in your rpm tachometer).
The dial measures psi and shows this with a needle.
I should have explained this more clearly at first.

Nylog is the stuff. It is cheap insurance for sealing things. It is used in the refrigeration industry as gospel. Use it on all your propane fittings from now on. Teflon tapes are of the past now unless you need to lubricate the threads..

I did not use Nylog on the tank fitting, possible that is a leak? I will go bubble check that and nylong it and retest.

**also, this tank I have had sitting in garage for 6+ months so I do not suspect it is leaking when closed.
Temps change very little overnight here during summer, not enough to swing psi this much.

If this is not normal then I will assume it is the pigtail, which is the only used part in the system other than the heater.

[dougrainer]

The LP standard for leak test is as follows.

Pressurize to 11 to 14 inches WC
Install the manometer
Lower the WC to about 8 inches wc
Measure the Manometer for 3 minutes
The system passes if no drop in pressure during the test.

There is no such thing as a completely sealed LP system. The system will leak down the LP in the system when the Tank is turned off over days/weeks.
YOU NEVER USE OR NEED TO USE ANY SEALANT ON A FLARE FITTING. NEVER!
If a flare leaks FIX the copper flare, do not attempt to use sealant. PIPE fittings, you use sealant/teflon tape. Doug

[Old-Biscuit]

RV Propane Leak Test.......

High Pressure Side (before Regulator)
Turn the main LP Gas Valve to the on position and listen for the initial PSST sound. After a second or two, the sound of flowing LP should stop.
Next step is to notice the green band in the clear regulator cap. Now turn the main LP gas valve off at the LP tank for
3 to 4 minutes.
Watch the green band in the clear regulator window, and it should stay green. If it turns red, (low gas indicator), this indicates a possible leak.

Low Pressure Side (after the Regulator)
Requires using a manometer connected to system.....stove top burner at manifold can be used
Valve in Propane Supply....verify system is 11"WC
Valve out Propane Supply...then slowly open burner knob and drop system pressure to 8"WC then close burner knob
Monitor pressure for 15 minutes....no change in system pressure then system is GOOD

System pressure drops....how fast will indicate size of leak
But only 15 minutes is required for leak down test on low pressure side
And only 3-4 minutes on high pressure side

Doubt you have a leak....indicator green/red is NOT a accurate means of testing

[Lynnmor]

Might be a very slow leak, but did you take temperatures into consideration?