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Old 04-09-2009, 10:39 AM   #1
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Water pump pressure/Hot water pressure relief valve ???

Does anyone know at what pressure the water pump turns "on" and what pressure the pump turns off ??

Also I just turned the hot water heater on this morning, first time since last nov.

Noticed just about as the water heater (gas oper.), was getting close to the turn off temp, the pressure relief valve started to "weep", seams to me I saw some where that's kinda normal ???

Shortly after the heater shutoff the weeping stopped.

Any comments etc appreciated.



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Old 04-09-2009, 07:14 PM   #2
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The pump pressure varies somewhat with the brand/model. A typical Shurflo will shut off at 45 psi and start at 25. The high end variable speed/constant pressure model holds 65 psi.

Follow this link, then click on "data sheet" for any model. The psi you're looking for is about half way down the page. If you don't have a Shurflo just google your brand for a similar page.

I'm not sure about the pressure relief valve, but believe it should be flipped from time to time, like when draining the tank. I live in a region where even the municipal water is well water and very hard. Most of us probably use at least moderately hard water when camping if it is drawn from a well and working this valve from time to time will help keep it moving freely.


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Old 04-09-2009, 08:32 PM   #3
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More to what Henry said about the relief valve on the HW tank...

When you first refill the system at the beginning of the season, it is very possible that there may be an air bubble in the tank. This can affect the pressures in the water system and make the pump perform exactly as you described.

Working the relief valve every once in a while is not only good to keep the valve working smoothly, but it will also hasten the elimination of the air bubble if there is one.

Without working the relief valve, the air bubble will eventually go away on its own, but it may take several days of regular useage for that to happen.

I have had to replace the relief valve on my home HW heater a number of times due to high mineral content in our water. Even the heavy duty softener we have doesn't eliminate all the minerals. For some reason, the minerals love to build up on the relief valve. If the valve isn't "exercised" (which cleans off mineral buildup), eventually, the minerals start a chemical reaction which eats part of the vavle assembly.

Now, unless you're full-timing in your TT, you likely won't move enough water through the HW tank to cause severe mineral buildup. But think about all the varying quality of water you might pump through there. Some CG's have great, soft water. Others is harder than a rock. It's possible to have some buildup over time.

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Old 04-09-2009, 10:08 PM   #4
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To add to what Steve has said:

A weeping HW relief comes from a few things. Some are:

1. The actual air pocket in the top of the heater that forms when filling occurs has diminished to almost nothing. This happens when the heater has been filled and stays full for a long time in use. When the air bubble dissolves there is no more expansion room left. When this occurs as the water heats thermal expansion occurs and the relief valve can weep to relive the thermal expansion built up pressure. Once the heat stops and it cools a little or the pressure drops, the weep stops. This is aggravated by a weak older valve and a valve that has sediment built up in the seat. To reform the air pocket, drain the heater and then just refill it.

2. As was mentioned, sediment builds up on the relive valve seat. Burping the valve with cooler water so you do not get burned can help reset it or make it leak worse sometimes if the build up is bad enough. Do not burp if fully hot or under high pressure. Water comes out that hole with authority. Ideally place some kind of old gutter or pipe up to the port are so it does not flood the electric control under it. And cover up your eyes with safety glasses.

3. The spring is weak. If you left the valve open with the handle up for a real long time, like over the winter, the spring can get weaker. The pressure these are set to trip at are 150 psi which is way above normal RV pump pressure unless the spring is weak.

4. The safety relief is set to trip at both temp and pressure and you generally get one with the other from thermal expansion. If your T stat is not working right and the heater is cutting out on high temp limit the water will be hotter then normal and can aggravate a week or sediment filled valve. This is not common but not beyond imagine. Is your hot water super hot? If so this is an indication the normal T stat is not shutting off the system when it is suppose to.

If you just came out of storage, filled it with water and did not flush it out prior to filling, I suspect no 2 above as the first possibly followed by then number 1. Over the winter, dry crusty minerals deposits fall to the tank bottom. Filling the tank stirs it all up and heads out the first available hole.

Good luck and hope this helps

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Old 04-10-2009, 07:10 AM   #5
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Thanks all for your input/info.

My camper was stored since last nov. I drained the hot water tank then.

The other day I filled, the fresh and hot water tanks as well as all the lines with water, running the pump. turned the hot water heater on (gas), and as I said before, about 5 minutes before the heater turned off the presure relief valve started slowley weeping. About five minutes after the water heater shut off, I noticed that the weeping had stopped.

I then turned the water heater to electric turning off the gas. Left it on all day running some hot water every now and then, checking the pressure valve several times and no more weeping at all.

I'm now wundering if a. there might have been some mineral deposits as you guys indicated ?

b.If there is some sort of seal and or gasket on the pressure relief valve that might have dried up over the winter, and now re-expanded, and then sealed better and therefore no weeping.

At any rated I'll continue to keep an eye on the pressure valve.

By the way I replaced the pressure valve a few years back, so this is not the original one the came with the camper when I got it new.

Thanks again

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