Water Heater Relief Valve

[Haffie]

Eric J,

Get a pressure gage and install it some where in the hot water system, maybe a threaded adapter for the kitchen faucet. See how high the pressure goes the first time you fire up the heater. Normal water pressure for a RV should be 45 to 55 pounds.

A lot of problems with those T&P valves is the washer dries up, cracks, sticks or just deteriorates after time.

Have a good one,

Haffie

[Mickey]

Haffie, the home water tank you described, a captive air tank, is a somewhat recent design. It was a design brought about to address the water logging that happened in earlier designs where the water did come in contact with the water. There were several intermediate designs to address the air defusing into the water.

Where we just moved from our tank was an old one. Not blue, not painted but galvanized. Had a small air pump attached to the tank to replenish the defused air but it didn't do the job completely and I had to manually add air several times a yr.

All the recent tanks I've seen have only had one opening into the tank so it is not possible for the check valve to be part of the tank. Check valve has to be located closer to the pump. On my well it was part of the foot valve located down in the well.

Now back to the RV. In all the RV's I've seen the WH tank serves as the accumulator. With no compressed air in the system the pump would have to run continually when water is flowing. The captive air also serves as a place for the water to expend in when heated. In my MH I have a small reserve provided by the air and can run water for short period without the pump running. No way could the plumbing expand to provide that reserve (~10 sec). One can add an additional accumulator to the system but they are not std for most RV's.

As for having for having air in the tank being dangerous, hogwash. Bacteria growth, not more of a problem than there was prior to captive air water tanks for the home. The air also provides a space for the heated water to expand into and the vol change is not great so any pressure increase is min.

Corrosion, that is why the steel tanks have a porcelain coating on the inside and why the aluminum tanks come with an anode. My MH is now 20 yrs old and I've never had issue with corrosion/leaks but then I also drain my water system after each use and my tank never gets water logged.

Guess we'll have to disagree on some things.

Where's Les, could use his comments.

[Mickey]

well yall got me scratching my head a lil bit here

One thing is fer sure, The pressure increases a good bit as it heats up.

.

Eric, pressure will increase quite a bit if there is no air in the tank/system. Water is incompressible so little change in vol due to heating will raise pressure. If there were air in the tank the water could expand into that area with little pressure change.

[Haffie]

Heya Mickey,

The one opening to the tank gets fitted with a "Tee". The center connected to the tank, one side to the house/rv plumbing. The other side gets the Check Valve between the tank and the pump, as close to the tank as possible.

After doing some on-line research, I guess we're both right to differing degrees. According to Atwood, their heaters are designed with the air-gap to use the heater as an accumulator (my bad).

Here is the procedure....

TO REPLACE THE AIR GAP FOLLOW THESE STEPS:
1. Turn off main water supply (the pump or water hook up source).
2. Let water cool or let run until cool.
3. Open the hot water faucet closest to the water heater.
4. Pull handle of pressure temperature relief valve straight out and
allow water to flow until it stops.
5. Allow pressure temperature relief valve to snap shut; close faucet;
turn on water supply.
6. Turn on water heater and test.
• At least once a year manually operate pressure-temperature relief
valve (FIG 10).
When pressure-temperature relief valve discharges again, repeat above
procedure. For a permanent solution, we recommend one of the following:
• Install a pressure relief valve in cold water inlet line to water heater
and attach a drain line from valve to outside of coach. Set to relieve
at 100-125 PSI.
• Install a diaphragm-type expansion tank in cold water inlet line.
Tank should be sized to allow for expansion of approximately 15 oz.
of water and pre-charged to a pressure equal to water supply pres-
sure. These devices can be obtained from a plumbing contractor or
service center.

I was taking most of my information from the last few paragraphs. Cut, Paste, Jiggle or whatever until everyone's happy.

I still stand by my comments as to the dangers of air and water mixing, especially if you don't know the source of the water you use to fill the water tank. Here in PA, a LOT of water is being polluted by "Fracking". A report released by the EPA, and they tried their damnest to keep it secret, shows the Fracking waste to contain excessive radiation levels. Water treatment plants cannot filter this out (along with other "goodies"), so it gets dumped into the rivers or forced back into the ground.

Irregardless, we at least woke this place up from it's winter hibernation

Have a good one,

Haffie

[Eric J]

well yall got me scratching my head a lil bit here

One thing is fer sure, The pressure increases a good bit as it heats up.

.

Eric, pressure will increase quite a bit if there is no air in the tank/system. Water is incompressible so little change in vol due to heating will raise pressure. If there were air in the tank the water could expand into that area with little pressure change.

Mickey that makes sense to me, I can agree with that.

and according to Haffies post of what Atwood says in step 6 I guess when I fill the tank (which I do by using the sink) I must be gettin all the air out leaving no expansion room in the tank? there for it pops the relief valve and from a cold start up, maybe that creates the longest burn and most pressure, I dont know? step 4 and 5 which I had no idea would create some expansion room, kinda make me think I would need to carrie a extra relief valve all the time. i,v seen enough of them pop and leak after they pop. being that i,m able to leave a drip at the sink on 1st heat up and it works fine after that, step 4 and 5 dont interest me none to much? I wonder just how level these lil water heaters have to be? or not be?

my mind has a hard time understanding just what in the world is goin to change by using steps 4 and 5? i,m goin to turn the same faucet back on at the same sink filling every thing back up again, I dont see how Atwood figures that?

The old water tanks talked about above I have lived with on a farm in W.VA and yes the would get water logged, they had a valve stem in the top of them, could run a air hose or simple use a tire pump and pump the pressure back up again after draining a lil bit of water out of them.

[Eric J]

Eric J,

Get a pressure gage and install it some where in the hot water system, maybe a threaded adapter for the kitchen faucet. See how high the pressure goes the first time you fire up the heater. Normal water pressure for a RV should be 45 to 55 pounds.

A lot of problems with those T&P valves is the washer dries up, cracks, sticks or just deteriorates after time.

Have a good one,

Haffie

Haffie I cant remember what I saw stamped on the relief valve? but i,m thinkin 125 to 150, the park pressure is 40 lbs at the camper so i,d say when it pops there is a heck of a lot more pressure than 45 lbs.

[Mickey]

Don't know what my WH mfgr says about draining or replenishing the air. My MH has drain valves for the water supply and both the cold and hot water lines. They have pull rings and are grouped together in an easy to reach place. I pop all 3 valves and open both cold and hot side faucets in the kitchen and bath. The whole system drains and drys. Never have an issue with freezing water lines or water in the WH and supply tank during the winter. When I refill the system upon next use I end up with maybe 25% of the WH tank as the compressed air "accumulator". Don't know if that is the approved way but has worked for me for more than 15 yrs.

[Haffie]

Mickey,

I don't think anyone, including the manufacturer's, have a definitive answer. Just keep doing what's always worked for you.

It does bother me that my water lines, faucets and toilet are exposed to pressures of 125psi and above though. That sounds like it's a potential bomb to me. The polybutylene pipe and fittings wouldn't stand that kind of pressure. I had one shut off valve "explode" with only 60psi in a tenant's home.

Have a good one,

Haffie

[Eric J]

I have 2 caps one on the hot and one on the cold to take off to drain the system may should put me some small ball valves on their? never thought about till now? but I cant tell if all the water would ever get out or not? the hot water tank I have to pull the anode rod (cant think how to spell that) out to drain the HW tank
I like the sounds of Mickeys much better

[Mickey]

Mickey,

I don't think anyone, including the manufacturer's, have a definitive answer. Just keep doing what's always worked for you.

It does bother me that my water lines, faucets and toilet are exposed to pressures of 125psi and above though. That sounds like it's a potential bomb to me. The polybutylene pipe and fittings wouldn't stand that kind of pressure. I had one shut off valve "explode" with only 60psi in a tenant's home.

Have a good one,

Haffie

I'm assuming with the pressure you're talking about city water pressure. If it were me, I'd add a pressure regulator to the input to drop the pressure down closer to what the system is intended for, ~45 psi.

I've seen a couple different designs for reducing pressure. The one design, the cheap ones, in my book aren't a pressure regulator but a flow restricter. Pressure will drop when water is flowing in these design but when flow is ZERO there is full line pressure. The more spendy kinds are pressure regulators. When talking pressure in a captive area, pressure is always greatest when flow is zero.

[Haffie]

Heya Mickey

I'm assuming with the pressure you're talking about city water pressure. If it were me, I'd add a pressure regulator to the input to drop the pressure down closer to what the system is intended for, ~45 psi.

No, that is a "suggested" solution from Atwood, in their instructions on how to rebuild the "air pocket" in the heater.

"• Install a pressure relief valve in cold water inlet line to water heater
and attach a drain line from valve to outside of coach. Set to relieve
at 100-125 PSI."

City water should be restricted to under 60psi using regulators or there would be a LOT of buildings turned into water falls. I personally use a regulator at the hydrant, then connect my fresh water hose. Then I have an in-line filter at the fresh water connector on my RV.

To me, it sounds like they assume the pressure will rise to that as the water and air heat up.

Have a good one,

Haffie

[Eric J]

City water should be restricted to under 60psi using regulators or there would be a LOT of buildings turned into water falls.

Haffie I am seeing where I live water pressure from 80 up to 100 lbs
The newest dryers that came out in the past 2 years now have a water valve in them to throw a light mist on the cloths, have had a few flood and I have to check house pressure and along with thermistors in washer water valves that pulse back and forth back and forth between hot and cold and just hammer the heck out of the water lines with pressure above 75lbs, the water company's will not help with it they are making house owners in stall there own regulators, I think they are trying to jam water through the water meeter so they can sell more every time ya turn a faucet on.
and I am seeing alot of the same type of blue and red plastic (crap pipe) as i call it, that my junker has in it and the darn stuff seems to be handling the pressure. I have a hard time believing it? but i,m sure seeing it.

[Haffie]

Eric J,

I guess there'll be a lot more of it as the Utility companies get municipalities to ban water wells to force home owners into using the utility company's water. I guess the home owner also has to pay to have the water line connected to the main.

All hell broke loose when the Mobile Home park I worked for dumped the 3 wells and connected to Utility water. Had to install a regulator and drop the pressure to 50psi. The main we hooked up to supplies water to the Fed. Pen. in Allenwood.

Have a good one,

Haffie

[jaaybird]

yuze guyz cornfused the HAIL of of me!!!!!

Took it to the shop bad pressure relief valve, $25.00 part
$20.00 labor.

[Rob98801]

yuze guyz cornfused the HAIL of of me!!!!!

Took it to the shop bad pressure relief valve, $25.00 part
$20.00 labor.

Right on.....K.I.S.S. works most of the time...

Enjoy the "new" water heater Jaaybird.