RV Blow Out Plug

[Old Duke]

Picked up an RV Blow Out Plug today to begin my winterization process. I see that the plug has a pressure restriction hole in the nipple. Is this for reducing the pressure during the blow out process? I have never used this type of plug before, always just reduced my pressures to about 20 psi with a regulator. I am assuming that I will not have to use a regulator with this new plug.... is that correct? My compressor regulator is set at 80 psi. Don't want to blow a hole in the system. Thanks for your help.

[WanderMore]

NO! You have to reduce you compressor output psi to 20-40. DO NOT inject 80 psi unless one of us there with a video camera for America’s Funniest Home Videos.

[rs2020]

Originally Posted by WanderMore

NO! You have to reduce you compressor output psi to 20-40. DO NOT inject 80 psi unless one of us there with a video camera for America’s Funniest Home Videos.

Bahahaha!!

[5picker]

Originally Posted by WanderMore

NO! You have to reduce you compressor output psi to 20-40. DO NOT inject 80 psi unless one of us there with a video camera for America’s Funniest Home Videos.

Wondering why you believe 80 PSI will blow things up?

When the air pocket gets depleted in the water heater, liquid expansion often causes pressures of 80 PSI and upwards. Some manufacturers say 150 PSI can be seen and that's why the T&P will drip at times.

Here's a photo of pressures I experienced last year while in FL. No explosions, no America's Funniest Videos!

[Oaklevel]

Gee I have never reduced the pressure in my air compressor in 35 years of camping and winterizing. I do keep the low point drains open though.........


Sorry no boom, no Americas Funniest Home Videos, no issues.


I have learned a lot on the internet of what I should not do though.......

[Mr. Dan]

Yeah… we have some old wives’ tales happening here.

[WanderMore]

Yes, it was a bit of exaggeration as pex is rated for about 480 psi if installed correctly. However, other items in the chain could suffer higher pressures if not properly installed or maintained. Best to approach maintenance items at recommended intervals and specified values.

[Old Duke]

What I am wondering is if the smaller hole in the blow out plug nipple (smaller than a normal 1/4" nipple hole) is used to restrict or regulate the pressure at the fresh water inlet. If it does, the pressure produced before the blow out plug can be 50, 60 or more psi and the smaller hole will only allow 20 to 30 psi into the water system. Same concept as the fresh water flow restrictors some people use at the fresh water inlet which is set at 50 psi.

[jmezz911]

I don't believe a smaller hole will regulate air pressure. It would only reduce the speed at which it gets up to that set pressure.

[TGR]

As jmezz911 said, while the faucets are closed, the air pressure will quickly build to the input pressure. The only time a restriction of this type would drop the air pressure is when air is going out of the system.

It is always safer to keep the input pressure down to a safe working level because compressed air, unlike water, acts like a spring storing energy when under pressure.

[jimmoore13]

Old Duke, you're on to something. It will reduce pressure ASSUMING A VALVE IS OPEN. But if you have all valves closed and you apply 80 PSI to the adapter, it will only take a bit longer to pressurize the rig's plumbing to 80 PSI than with a conventional 1/4" quick connect. A small orifice reduces VOLUME not PRESSURE in a static system.

What this adapter WILL do is cut down on CFM from the compressor to the rig's plumbing...something that is decidedly NOT helpful.

I use a conventional adapter that I made from two hardware store parts - both brass: a 3/4" male hose thread to 1/2" female NPT thread combined with a conventional 1/4" air quick connect with 1/2" NPT male thread on the other end. My home-made adapter probably cost 3 times as much as the one in the link provided below.

I set my compressor to 45 to 50 PSI (it's an approximation...the compressor regulators are not precision tools), and I connect the air to the rig. With the compressor regulator set to 45 to 50 PSI, this emulates the pressure allowed by a hose end pressure regulator you buy to connect your rig to "city water" connections at an RV park.

With this setup, I'm able to connect the air with NO OPEN VALVES, and when the rig's plumbing reaches about 50 PSI, air stops flowing until I open a valve. This includes the low point drains. If the low point drains remain open at all times, this can bleed off a huge amount of the available air pressure and volume. Treat those like any other valve, and only open them when it's their turn.

But CFM is crucial to a thorough blowout. With a "pin-hole" adapter, there isn't enough air flow to purge the rig's plumbing of water. The 1/4" opening allows LOTS of CFM at modest pressure, and the rig is blown dry quickly and easily. Frankly, if you had 3/8" connectors and a compressor capable of delivering that much air at 50 PSI, that would be even better. Remember that the lines inside the rig are all 1/2", so you immediately reduce the CFM by half when you jump from 1/4" air adapter to 1/2" pex. (This is another reason it's good to shut off ALL valves for a moment until the rig is fully pressurized with air.)

Others are fond of saying the plumbing can handle more pressure...and that may be so. Every system is built with considerable headroom for safety. But there's a reason you add a pressure regulator on the end of your potable water hose. Even your house...connected to city water...has a pressure reducer...often down to about 60 PSI. It keeps things from breaking...such as those $2 plastic faucets and shower heads in the rig. PEX might be tough, but the faucets and other plumbing "hardware"? Not so much.

Moderate pressure at high CFM volumes is the most efficient way to use air to winterize your rig. If that adapter is plastic, get out your drill and 1/4" bit...if not, buy a new one. And continue running your compressor around 40 to 50 PSI. That pressure is more than enough...and it's what's recommended based on the water pressure regulator you use.

P.S. My full winterization process involves, isolating the hot water heater with the bypass valves (and draining it), then rotating from valve to valve repeatedly...about 4 times each...until everything is bone dry. This list includes kitchen and bathroom sinks, shower/tub, toilet flush, outside shower, low point drains. Again, one valve at a time over and over again. This takes only a couple minutes. Then I blow out the black tank flush. Next I attach a blow gun to the air hose, open the lid to the water pump compartment, switch the valve to the RV antifreeze siphoning position and blow air thru the pump, and then return that valve to draw from the fresh tank. Meanwhile both the hot water heater and the fresh tank are draining.

I leave the drain valves for the fresh tank and low point drains open for the winter just in case a few drops trickle down to the valves. If you are worried about vermin entering through the open valves, stuff a tiny bit of screen into the open ends of the valves.

[Larry-NC]

Originally Posted by jmezz911

I don't believe a smaller hole will regulate air pressure. It would only reduce the speed at which it gets up to that set pressure.

Exactly! A restriction in size does not change static pressure, only flow rate. Stop and think for a second about what happens if all valves are closed and the orifice is only a pinhole. The static pressure throughout the system will stabilize to the source pressure.

I'm not sure how anyone would winterize by blowing out the system with low point drains open. There's no guarantee that all branches will drain at all. If you're going to winterize by blowing out the system, you need to turn everything off and then open one tap at a time until each is dry.

And as 5-Picker noted, the plumbing is capable of much more than 40-50 psi.

[Old Duke]

Jimmore13, thank you for your response. Have read it several times, and digested all. Very well written and helpful. This was the answer I was looking for. Regulator at 30 psi as usual........

[NMWildcat]

Oh dang. The water pressure at my house is usually around 75psi and I hook up my RV water with no regulator. My new fancy RV water pump is 55psi and 4gpm flow. My high flow pressure regulator is 55psi. I blow out my RV with 60 psi.
Been doing this for 10 years with this RV. Still waiting for it to blow up as it sounds like it should be spectacular to watch!!!

[camaraderie]

While pix is designed to hold much more...I'm afraid the joints & or clamps in the system are NOT either from the factory or over time and since 40-50 lbs. is both safe and effective pressure to blow out the system ...that's where I set it. No harm no foul.

[DouglasReid]

Originally Posted by jimmoore13

Old Duke, you're on to something. It will reduce pressure ASSUMING A VALVE IS OPEN. But if you have all valves closed and you apply 80 PSI to the adapter, it will only take a bit longer to pressurize the rig's plumbing to 80 PSI than with a conventional 1/4" quick connect. A small orifice reduces VOLUME not PRESSURE in a static system.

What this adapter WILL do is cut down on CFM from the compressor to the rig's plumbing...something that is decidedly NOT helpful.

I use a conventional adapter that I made from two hardware store parts - both brass: a 3/4" male hose thread to 1/2" female NPT thread combined with a conventional 1/4" air quick connect with 1/2" NPT male thread on the other end. My home-made adapter probably cost 3 times as much as the one in the link provided below.

I set my compressor to 45 to 50 PSI (it's an approximation...the compressor regulators are not precision tools), and I connect the air to the rig. With the compressor regulator set to 45 to 50 PSI, this emulates the pressure allowed by a hose end pressure regulator you buy to connect your rig to "city water" connections at an RV park.

With this setup, I'm able to connect the air with NO OPEN VALVES, and when the rig's plumbing reaches about 50 PSI, air stops flowing until I open a valve. This includes the low point drains. If the low point drains remain open at all times, this can bleed off a huge amount of the available air pressure and volume. Treat those like any other valve, and only open them when it's their turn.

But CFM is crucial to a thorough blowout. With a "pin-hole" adapter, there isn't enough air flow to purge the rig's plumbing of water. The 1/4" opening allows LOTS of CFM at modest pressure, and the rig is blown dry quickly and easily. Frankly, if you had 3/8" connectors and a compressor capable of delivering that much air at 50 PSI, that would be even better. Remember that the lines inside the rig are all 1/2", so you immediately reduce the CFM by half when you jump from 1/4" air adapter to 1/2" pex. (This is another reason it's good to shut off ALL valves for a moment until the rig is fully pressurized with air.)

Others are fond of saying the plumbing can handle more pressure...and that may be so. Every system is built with considerable headroom for safety. But there's a reason you add a pressure regulator on the end of your potable water hose. Even your house...connected to city water...has a pressure reducer...often down to about 60 PSI. It keeps things from breaking...such as those $2 plastic faucets and shower heads in the rig. PEX might be tough, but the faucets and other plumbing "hardware"? Not so much.

Moderate pressure at high CFM volumes is the most efficient way to use air to winterize your rig. If that adapter is plastic, get out your drill and 1/4" bit...if not, buy a new one. And continue running your compressor around 40 to 50 PSI. That pressure is more than enough...and it's what's recommended based on the water pressure regulator you use.

P.S. My full winterization process involves, isolating the hot water heater with the bypass valves (and draining it), then rotating from valve to valve repeatedly...about 4 times each...until everything is bone dry. This list includes kitchen and bathroom sinks, shower/tub, toilet flush, outside shower, low point drains. Again, one valve at a time over and over again. This takes only a couple minutes. Then I blow out the black tank flush. Next I attach a blow gun to the air hose, open the lid to the water pump compartment, switch the valve to the RV antifreeze siphoning position and blow air thru the pump, and then return that valve to draw from the fresh tank. Meanwhile both the hot water heater and the fresh tank are draining.

I leave the drain valves for the fresh tank and low point drains open for the winter just in case a few drops trickle down to the valves. If you are worried about vermin entering through the open valves, stuff a tiny bit of screen into the open ends of the valves.

X2 to ALL the above!!