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Old 01-27-2017, 10:51 AM   #15
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Quote:
Originally Posted by firedoc View Post
I have never heard of the nylon plug blowing out before. Did it blow out the center of the plug and leave the threads in the heater? A picture would have been very interesting. I wonder if that's why they often sell those plugs in a two pack? Defective plug? What would have caused it? Lots of questions.

Also in filling the water heater it was my impression that you take out the pressure relief valve and fill till water reaches the port, then replace the valve and fill the rest of the way to get the air gap.
I have had the nylon plug leak, but not blow off. i would have thought the pressure relief valve would have lifted before the plug blew out especially in the dramatic fashion it did.

When I dewinter the RV, i open the hot water faucet in the coach and when I get cold water through I beleive the tank is full!
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Old 01-27-2017, 10:57 AM   #16
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Quote:
Originally Posted by firedoc View Post
I have never heard of the nylon plug blowing out before. Did it blow out the center of the plug and leave the threads in the heater? A picture would have been very interesting. I wonder if that's why they often sell those plugs in a two pack? Defective plug? What would have caused it? Lots of questions.

Also in filling the water heater it was my impression that you take out the pressure relief valve and fill till water reaches the port, then replace the valve and fill the rest of the way to get the air gap.
NYLON plugs.......
2 pack because they are disposable. After a few removals they can become damaged....either the threads or the hex head.

No telling what can of shape OPs was in prior to blowing out.
Could have been cracked, threads could have been stripped from cross-threading.
T&P doesn't OPEN until 150PSI or 210*F
T-stat opens at 140*F (ECO-HI temp opens at 180*F)



Filling water heater...
By design an air pocket will form at top of tank during normal filling of water heater.
No need to open T&P, no need to remove T&P, no need to do anything special.
Just turn on water supply and open a faucet hotside to bleed air out of system.

Sometimes the air pocket will get lost and needs to be re-established.
Weeping from T&P is indication of a lost air pocket

Turn water supply OFF
OPEN nearest faucet hotside to relieve system pressure
OPEN T&P Relief Valve via lever----hold open until water stops
CLOSE T&P by letting it snap shut
CLOSE faucet
Turn on water supply
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Old 01-27-2017, 01:21 PM   #17
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Since the drain plug blew out, I would be very concerned that the PT (Pressure-Temperature) relief valve is stuck closed. That's a serious risk - the tank itself would have exploded if the plug hadn't gone first. I would replace the PT immediately, even if it appears to be working now. It's a standard heater PT, available at most any home center or hardware store.
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Old 01-27-2017, 01:33 PM   #18
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Quote:
Originally Posted by firedoc View Post
I have never heard of the nylon plug blowing out before. Did it blow out the center of the plug and leave the threads in the heater? A picture would have been very interesting. I wonder if that's why they often sell those plugs in a two pack? Defective plug? What would have caused it? Lots of questions.

Also in filling the water heater it was my impression that you take out the pressure relief valve and fill till water reaches the port, then replace the valve and fill the rest of the way to get the air gap.
Never heard of that before. I have heard of folks opening the valve to let more water in. Also not a good idea.
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Old 01-27-2017, 02:48 PM   #19
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Originally Posted by Gary RVRoamer View Post
Since the drain plug blew out, I would be very concerned that the PT (Pressure-Temperature) relief valve is stuck closed. That's a serious risk - the tank itself would have exploded if the plug hadn't gone first. I would replace the PT immediately, even if it appears to be working now. It's a standard heater PT, available at most any home center or hardware store.

Water would have to have been EXTREMELY HOT........210*F PLUS for T&P Relief Valve to OPEN.

That would mean BOTH t-stat AND ECO had failed to shutdown heating process.......possible that is reason for T&P but doubtful.

Most likely is drain plug was faulty due to being old & cracked

BUT if OP wants to change out their T&P Relief Valve they need to measure it.
OPs RV is a 2002...so T&P should be a 1/2" NPT short probe T&P
Atwood changed sizes in 2004.......since then 3/4" NPT are used.
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Old 01-27-2017, 08:50 PM   #20
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When filling the water heater you leave the pressure relief valve CLOSED! This establishes the correct expansion space in the tank.
Mr_D, this is from the Atwood manual, a direct copy and paste!

PRESSURE-TEMPERATURE RELIEF VALVE Weeping or dripping of a pressure-temperature relief valve while the water heater is running DOES NOT mean it is defective. This is normal expansion of water as it is heated in the closed water system of a recreation vehicle. The Atwood water heater tank is designed with an internal air gap at the top of the tank to reduce the possibility of weeping and dripping. In time, the expanding water will absorb this air. To replace the air follow these steps: Step 1: Turn off water heater Step 2: Turn off incoming water supply Step 3: Open the closest hot water faucet in the coach Step 4: Pull handle of pressure-temperature relief valve straight out and allow water to flow until it stops.Step 5: Allow pressure-temperature relief valve to snap shut, turn on water supply and close faucet.

I would add one more step, allow the water heater to cool, before you open the pressure-temperature relief valve, as the water may be hot, if you have had the WH on!

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Old 01-27-2017, 10:03 PM   #21
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Mr_D, this is from the Atwood manual, a direct copy and paste!

PRESSURE-TEMPERATURE RELIEF VALVE Weeping or dripping of a pressure-temperature relief valve while the water heater is running DOES NOT mean it is defective. This is normal expansion of water as it is heated in the closed water system of a recreation vehicle. The Atwood water heater tank is designed with an internal air gap at the top of the tank to reduce the possibility of weeping and dripping. In time, the expanding water will absorb this air. To replace the air follow these steps: Step 1: Turn off water heater Step 2: Turn off incoming water supply Step 3: Open the closest hot water faucet in the coach Step 4: Pull handle of pressure-temperature relief valve straight out and allow water to flow until it stops.Step 5: Allow pressure-temperature relief valve to snap shut, turn on water supply and close faucet.

I would add one more step, allow the water heater to cool, before you open the pressure-temperature relief valve, as the water may be hot, if you have had the WH on!

Rail!
Correct .........
BUT procedure is HOW TO RE-ESTABLISH air gap after it has been lost due to absorption into the heated water. Weeping form T&P is indication of that loss of air gap.

Initially the air gap is established by just normal filling of water by turning on water supply and bleeding air out of system by opening a faucet hotside.

Air is left in top of tank due to HOT out dip tube position .........lower than tank top leaving natural air gap area

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Old 01-27-2017, 10:30 PM   #22
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I'll see if I can find the plug that blew off to post for y'all. I'm slightly freaked out by it since that happened, so I just shut it off when I'm not showering. It is working perfectly now, but the whole thing was traumatizing.

So Gary, you think my Pressure Temp Relief Valve may not be working properly? Is it difficult to swap out?

I don't know if this contributed (I suspect it did) but I accidentally left the water heater on after we ran out of water. It was on for a few hours at least When we refilled the water, I noticed it was on and turned it off. Then about an hour later BOOM it went.

I'm doing a stellar job at wrecking my lovely coach. I don't know what I'd do without y'all guiding me through this. Thank you so much!
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Old 01-27-2017, 11:08 PM   #23
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Correct .........
BUT procedure is HOW TO RE-ESTABLISH air gap after it has been lost due to absorption into the heated water. Weeping form T&P is indication of that loss of air gap.

Initially the air gap is established by just normal filling of water by turning on water supply and bleeding air out of system by opening a faucet hotside.

Air is left in top of tank due to HOT out dip tube position .........lower than tank top leaving natural air gap area

Old-Biscuit, no disrespect, but you are splitting hairs, Dang, Re-establishing a air gap, or opening the T&P, is the same! Why wouldn't it be the same as just filling it up to the water line of the T&P? What, from that drawing about a inch or so? Dang, splitting hairs! After the water heats up and expands, the air gap will go to the hot water dip tube anyway! And you are assured that you will have room for the water to expand!
Either way will work, but for me, opening the T&P, till the water comes out, snapping it shut, gives me the satisfaction of knowing the air gap is there! Plus, opening the T&P valve, and snapping it shut a couple of time's is good for it. JMHO! Rail!
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Old 01-28-2017, 06:19 AM   #24
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I'm wondering if someone went gorilla on the nylon plug and cracked it when they de wintereized. If they needed to use an extractor then the top was gone but the body was still threaded in.
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Old 01-28-2017, 10:33 PM   #25
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I'm wondering if someone went gorilla on the nylon plug and cracked it when they de wintereized. If they needed to use an extractor then the top was gone but the body was still threaded in.
That is what happened to mine,only thing left was the threads.
Was able to pry the threaded part out with a small wood chisel.
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Old 01-29-2017, 08:58 AM   #26
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Old-Biscuit, no disrespect, but you are splitting hairs, Dang, Re-establishing a air gap, or opening the T&P, is the same! Why wouldn't it be the same as just filling it up to the water line of the T&P? What, from that drawing about a inch or so? Dang, splitting hairs! After the water heats up and expands, the air gap will go to the hot water dip tube anyway! And you are assured that you will have room for the water to expand!
Either way will work, but for me, opening the T&P, till the water comes out, snapping it shut, gives me the satisfaction of knowing the air gap is there! Plus, opening the T&P valve, and snapping it shut a couple of time's is good for it. JMHO! Rail!
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I defense of Old Biscuit...IMO posting correct information is not "splitting hairs".

Because an air pocket will form at the top of RV water heater tank during normal filling of the water heater tank...."Opening the T&P, till the water comes out", is not necessary when filling the tank.

However I agree that "opening the T&P valve, and snapping it shut a couple of time's is good for it".

I do that each time I drain the water heater tank..(not while filling it).
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