Water pump & line pressure

[Petrovsky]

A general question. Why would the pressure drop over 15+ hours in the water system after you shut the water pump: note that the water heater had not been used and is cold. Of course over the space of a number of hours the system retains pressure (water heater cold and hot as tested). However, starting with a cold water heater, after an overnight shut down the water pump kicks in to restore pressure. I have opened up as much as I can to look for leaks and have not seen any. Have not looked in the underbelly but have tapped it to see if some water might have accumulated. Nothing.

The water pump is a SHURFLO 4008-101-A65 New 3.0 GPM RV Water Pump Revolution, 12V

It has an internal pressure bypass.

My previous TT only cycled a bit as the water in the water tank cooled (there were no leaks). Of course it would not maintain system pressure indefinitely come to think of it, but I don't think the pump kicked in after 15 hours with a cold non-heated water tank (sold it so can't test that).

I might be reading too much into this but with the pex to braided line issues my previous TT was all pex I just wanted some opinions.

[Country Campers]

If the pressure would drop to zero then I would think you would have a leak , not saying that you do not have one. The temperature change as well as low or high pressure weather could affect the pressure as well. The soft hose would expand when pressure is applied so it would kind of "hold" pressure. There are plenty of fittings in your RV that could have a small drip that would cause the pump to cycle but finding it cold be a chore. Check behind the water inlet panel , also at the pump , under all of the sinks , behind toilet , if not any of those places then you will have to go under the belly which is a whole nother mess. After using water from the pump and not running any water for a while I have heard mine run a small little amount , 1 or 2 seconds , and then nothing for hours but I have not sat for hours very often to hear if it runs every once and a while.

Brian

[Yoda]

A general question. Why would the pressure drop over 15+ hours in the water system after you shut the water pump: note that the water heater had not been used and is cold. Of course over the space of a number of hours the system retains pressure (water heater cold and hot as tested). However, starting with a cold water heater, after an overnight shut down the water pump kicks in to restore pressure. I have opened up as much as I can to look for leaks and have not seen any. Have not looked in the underbelly but have tapped it to see if some water might have accumulated. Nothing.

The water pump is a SHURFLO 4008-101-A65 New 3.0 GPM RV Water Pump Revolution, 12V

It has an internal pressure bypass.

My previous TT only cycled a bit as the water in the water tank cooled (there were no leaks). Of course it would not maintain system pressure indefinitely come to think of it, but I don't think the pump kicked in after 15 hours with a cold non-heated water tank (sold it so can't test that).

I might be reading too much into this but with the pex to braided line issues my previous TT was all pex I just wanted some opinions.

It could also be leaking past the check valve back to the fresh water tank. Only way to know for sure is to install a valve in the feed line, which could somewhat easily be done with the correct fittings at the water pump (intake side). Just brainstorming here.
Keith

[TedS]

It could also be leaking past the check valve back to the fresh water tank. Only way to know for sure is to install a valve in the feed line, which could somewhat easily be done with the correct fittings at the water pump (intake side). Just brainstorming here.
Keith

The better place for the test check valve would be in the pump outlet plumbing.

[Cate&Rob]

Petrovsky
Hi Pierre,

Unless you have a puddle accumulating somewhere, I would agree with the “leaking check valve in the pump” theory. I have posted (many times) on the value of a simple “system” pressure gauge. This will tell you what is going on. The simplest temporary installation for this gauge is to attach it to the cold water low point drain.

Rob

[Petrovsky]

Thanks for the input. I too was suspecting the possibility of the leaking check valve theory. As mentioned by Brian above, my pump comes on for about 3 seconds. It isn't from a full depressurized state. I have paper towels at all connections and they are dry. The new Dometic heater has a "nylon" cap instead of a plug. It is wet but no accountable dripping, I will get rid of it and use an FTP (NPT) plastic cap on it rated up to 150°F. I will remove the access below the shower a put some paper towels in line with the hoses going up to shower taps. Pretty much exhausted checking topside. Have not checked the water access bay but if it were leaking there, buy now I would have seen evidence as there is a list of 3° forward so water would have sneaked under the panel. On second thought, I will remove the access just to see how it is plumbed.

No puddles noted of any kind so maybe in the underbelly....not where I can easily check without major work. I saw a post of someone one that had found a small leak in the underbelly of a 2600 but can't recall where. He had indicated in the post the rough location of the two (hot & cold) tee connections. It is sealed up so nicely right now...so this is last resort checking. I know the lines going into the underbelly are braided hose and not pex.

If anything major comes up I have added to my tools and supplies following Cate & Rob's suggestions. I have an air compressor and an independent pressure regulator with gauge. Could always check the bleed of time starting a 45 psi.

Thanks for the suggestions. We have a camping test run scheduled in Ontario next week when the border (Quebec/Ontario) opens up. Although water is on the site.....I will fill the tank and use that instead to monitor situation. Most of our camping is with electrical service only.

Will keep you posted. Already have fixed a few things.....no time to leave this at dealer's and frankly he has no availability anyways so best do the work myself.

[Cate&Rob]

Petrovsky

Install the pressure gauge! The best $15 ($20 Cdn ) that you can spend on figuring out water pressure questions.

Rob

[Petrovsky]

Petrovsky

Install the pressure gauge! The best $15 ($20 Cdn ) that you can spend on figuring out water pressure questions.

Rob

Rob,

Will order one. Will be less trouble to hook up than the air pressure and attaching to cold water low point drain will be quite easy. I will be removing the plugs and installing valves instead this summer.

Thanks

Pierrre