Accumulator Tank

[TedS]

I will be installing this accumulator when the weather gets warmer.

[Cate&Rob]

TedS

If you are going to install an accumulator tank (which is a good idea BTW) why not install a much larger one? I went with a 2 gallon residential one that has 10 times the volume of the 0.75L one for about the same cost. It was not difficult to find room behind the wall in the pass through storage area.

Rob

[TedS]

Cate&Rob,
The expansion of the hot water is around 8 oz so the 23 oz volume is enough. I set the pressure to 50 to 60 psi and don't use it to augment the pump.

[Jlawles2]

Cate&Rob are you using it to augment the pump to mitigagte short cycling of the pump? What preset pressure are you using?

Hopefully they have changed the plumbing lines to all PEX by now. If not, I will look at changing the fittings first.

Any reason why you went PEX B with clamp rings vs PEX A with the expanding collars/ Tooling looks to be a wash, fittings on the A are full bore thus less water flow restrictions.

[Cate&Rob]

Cate&Rob are you using it to augment the pump to mitigagte short cycling of the pump? What preset pressure are you using?

Hopefully they have changed the plumbing lines to all PEX by now. If not, I will look at changing the fittings first.

Any reason why you went PEX B with clamp rings vs PEX A with the expanding collars/ Tooling looks to be a wash, fittings on the A are full bore thus less water flow restrictions.

I do use the accumulator tank to avoid short cycling the pump and to absorb pressure rise from water heating. This tank can be T'd into any convenient cold water supply line.

As I have recommended on several previous threads, installing a system water pressure gauge will tell you a lot about what's going on. Before the accumulator tank, I could watch system pressure climb past 70 psi, following the common process of connecting to the campground water system and then turning on the water heater without opening a faucet to relieve pressure as the water heats up. Many think that the pressure on the gauge at their inlet hose regulator is their water system pressure . . . it is not. With the accumulator tank, pressure rise due to water heating is negligible.

I set the accumulator pressure to just below the pump cut-in pressure. (This is easy to see/adjust with the gauge described above) About 30 psi. Thus, the pump comes on just before the accumulator tank is empty. This means that the pump comes on less frequently (and can be shut off at night while allowing toilet flushes) and runs for longer when it comes on. Both are good things for a pump.

I chose to continue with the stainless steel Pex clamp rings used by Grand Design to be consistent with the rest one the plumbing (one set of tools and parts). These clamp rings are also easier to remove than the copper rings. Grand Design has no intention of removing the soft hose. This expedites their production process making routing and connections easier and faster during assembly. Not much chance of seeing an "all Pex" build.

Rob

[Country Campers]

Moderator note.
Moved these post to keep the original thread on track.

Brian

[Jlawles2]

Cate&Rob So the way I see it, the pressure regulator acting as a 1 way valve is causing excessive pressure in the plumbing system of the unit. Never realized that could be an issue. Also when dry camping the onboard pump put just enough pressure in the system and has a 1 way valve in it that creates the same excessive pressure. Would be nice if somehow this excessive pressure could be vented safely to prevent issues with onboard plumbing lines.

Rob, i was referring to the white expansion sleeve PEX A system vs the Pex B system that uses either the round copper compression bands or the humped crip collars. The plumbers that redid our house used PEX A and I have learned that those systems are a bit more forgiving in the fittings since the ID of the fitting is the same ID as the pipe. Tool size is a wash for storage requirement as they are about the same size. I did see an interesting note from a plumber that stated sometimes its easier to use the A b/c of space constraints getting the crimp tool in.

[Cate&Rob]

Jlawles2

Both the city water connection and the on-board pump outlet have check valves that will prevent back flow and thus hold pressure in the system. The water heater has an air space at the top to absorb expansion and a pressure relief valve which is the “safety” for pressure rise due to water heating. My 2 gal accumulator tank now absorbs this water expansion with minimal pressure increase.

I have never worked with Pex A. Only the clamped B or C as used originally by Grand Design. Flow restriction due to fittings is interesting. It makes sense that this should happen, but in my experience it is not significant. When I removed the soft hose, I routed the Pex through many more elbows and connectors in preparation for having to one day remove the furnace which has no external access panel on my early build Reflection. I was prepared for significant flow reduction . . . but, there was hardly any change from the previous smooth run of soft hose.

Rob

[bogen2]

TedS

If you are going to install an accumulator tank (which is a good idea BTW) why not install a much larger one? I went with a 2 gallon residential one that has 10 times the volume of the 0.75L one for about the same cost. It was not difficult to find room behind the wall in the pass through storage area.

Rob

Rob,

I like the mounting system system you designed for this. What tank did you go with? Anything to watch for when choosing a residential tank for an RV?

Does the tank drain when the low point drains are opened?

Bob

[Jlawles2]

Cate&Rob Rob, do you need to "TEE" into a line, or can it be blocked on one port?

[Cate&Rob]

Rob,

I like the mounting system system you designed for this. What tank did you go with? Anything to watch for when choosing a residential tank for an RV?

Does the tank drain when the low point drains are opened?

Bob

Hi Bob,

Any small residential accumulator tank will do the job. Choose one with a diaphragm (sometimes called a bladder) to keep the air from dissolving into the water. Most residential accumulators have this. The small boat/RV ones do not. Because of the diaphragm, the accumulator does not have to stand vertically . . . but, this makes sure that it drains completely when the low point drain is opened. when I rebuilt my plumbing system. I stood this accumulator on end (as I would do in a residential installation) and someone on this forum pointed out that this didn't look very secure for an RV. I had to agree . . . so, I added the support in the forward direction (because my disc brakes stop this thing in a hurry when necessary )

Rob

[Cate&Rob]

Cate&Rob Rob, do you need to "TEE" into a line, or can it be blocked on one port?

The accumulator can be connected anywhere in the cold water supply system. Because it would usually be connected into an existing line . . . this would be a "Tee" connection. I am not sure what you mean by "blocked on one port" ? . . . there is only one water connection to an accumulator tank.

Rob

[TedS]

I will be installing my accumulator with the ports vertical and cap the upper port. The lower port will be connected to a T in the pump outlet line, the common cold water input. The accumulator does have a diaphragm separating water from air. This accumulator can be installed in a line as a T, water passing through port to port.

[Jlawles2]

Rob, I saw a couple with a built in Tee on the inlet of the tank like the one posted by the OP. I would not think that the system would care if the other end was capped or not.

[Cate&Rob]

Rob, I saw a couple with a built in Tee on the inlet of the tank like the one posted by the OP. I would not think that the system would care if the other end was capped or not.

If the accumulator tank has a built in Tee and you choose not to use it, one side could be capped, leaving a single water connection, like a residential accumulator. The time between pump cycles will be a function of the size of the accumulator tank. A small tank will provide only a momentary break between pump cycles. If I had room for a larger accumulator tank, I would choose that. On my boat, I installed two 2 gal accumulator tanks, because this best fit the space available.

Rob