To accumulate or not?

[Tom]

Thanks Rex. Didn't realize that hardware stores sold accumulator tanks that would work on the coach.

 

[N Smock]

Tom


The extra hose that Karl pointed out works good. I have done that on my TT and 5er. The parts are available at Lowes, a little reinforced PVC barb fittings and clamps and you are in business. This uncouples the pump vibration from the semirigid coach plumbing. This probally a cheaper and easier solution than adding an accumulator tank.


Nelson

 

[Gary RV_Wizard]

Didn't realize that hardware stores sold accumulator tanks that would work on the coach.

I don't think the physics of a water system change just because its in an RV, despite the myriad of special "RV" products on the market. 

 

[Tom]

I don't think the physics of a water system change just because its in an RV, despite the myriad of special "RV" products on the market.

LOL Gary, I probably didn't clearly say what I was thinking. I wasn't aware that any accumulator tanks were used in homes. So it didn't occur to me that a hardware store would sell the kind of accumulator tank we're talking about for an RV.

The "above tank" that I previously recalled being used in homes in the UK was simply a non-pressureized tank that provided a head of water. That, of course, was 30+ years ago and not too long after we were still using outhouses.

 

[Tom]

Nelson,

I'm going to have to try the flex hose approach on the coach and the boat. In the latter case, the clank, clank, thump, thump used to drive me nuts and the local dealer couldn't fix it. I complained hard enough for the manufacturer to fly someone out from Florida to California. He spent a couple of days working on it, including enlarging holes where the water lines ran through bulkheads. The only positive thing he did was install a larger accumulator, which helped. But, when the pumps come on, the noise is still there. I assumed that there's some length of unsupported water line (e.g. behind the shower) that is amplifying the pump vibration/sound.

 

[AlGriefer]

Nelson,

I'm going to have to try the flex hose approach on the coach and the boat. In the latter case, the clank, clank, thump, thump used to drive me nuts and the local dealer couldn't fix it. I complained hard enough for the manufacturer to fly someone out from Florida to California. He spent a couple of days working on it, including enlarging holes where the water lines ran through bulkheads. The only positive thing he did was install a larger accumulator, which helped. But, when the pumps come on, the noise is still there. I assumed that there's some length of unsupported water line (e.g. behind the shower) that is amplifying the pump vibration/sound.

Just a thought; the pump on the boat made a whole lot of noise until we unmounted it and remounted it on pieces of heavy rubber hose using them as shock absorbers.

How is the pump mounted to the coach?

Al

 

[Tom]

Al,

The pumps on the boat came from the factory mounted on short lengths of flexiblle PVC sewer hose. I just checked the pump on the coach and it's hard mounted to the plastic wall of the utility bin. Might as well put it in a speaker enclosure 

 

[AlGriefer]

Might be worth remounting it?

Al

 

[Tom]

Yes it would Al. But, when I saw the mounting on the side wall, I realized I'd also need to extend the lines. Might be time to add the flex line extensions.

 

[AlGriefer]

True enough!

 

[PancakeBill]

I just replaced my pump with a ShurFlo VSD.  Love it.  Nice and quiet, great water flow and at low flow no pulsing.  Works just like the home faucet!  Had an accumulator on the old camper, and while it is true that a small demand will have no pump, once it drops, the pump runs until the pressure is back. 

Also true the pump is way more than a regular pump, but these things seem to last forever.  If it lasts 5 years, (will the coach?), it was a cheap investment.  I am using the old pump in my utility trailer for wash down. 

 

[Tom]

Thanks for the report Bill. I assume you don't need or use an accumulator with the VSD (?)

 

[Karl]

There are several different accumulator or pressure tanks available which may or may not be suitable for RV use. Eliminating the ones too large for an RV, we're left with the ones that are up to approximately 6 gallon size; similar in size to a standard RV hot water heater. Reviewing the manufacturers installation instructions, they all say that they can be installed in any position. While this may be true, there may be an optimal position which will allow maximum draw without the pump cycling. Shurflo states that it is best to install it with the bladder (diaphragm) charge valve on top to allow for the best drainage for winter storage. Yes, this is true, but it may not be the best installation position for regular use. I have included a document to illustrate. In Figure 1, the charge valve is at the bottom; in Figure 2 it is at the top. When initially filling the system with water, you can see that the accumulator, as shown in Figure 1, will fill almost completely with water and allow the air to escape when faucets are first used, while the installation in Figure 2 will trap excess air in the top of the accumulator, which will reduce the draw down and cause the pump to cycle more frequently. Over time, this excess air will be absorbed into the water, but that may take quite some time and reduce the benefits of the tank until this happens. My suggestion is that you install it with flexible hose, and initially charge the system (hooking it up to shore water or refilling from the tank after returning to use after winter storage) with it in the Figure 1 position, and leave it that way for the duration of your RV'ing season. If you are going to winterize, dismount it and turn it to position as shown in Figure 2 so that all water drains from the tank. I've only shown the two vertical positions, but you can see how much excess air will be trapped by a horizontal mounting; somewhat less than half the tank capacity. Yes, any position will work, but not all will work equally well!

 

[Alaskansnowbirds]

I wasn't aware that any accumulator tanks were used in homes. So it didn't occur to me that a hardware store would sell the kind of accumulator tank we're talking about for an RV.

Tom,

Any home that is heated with a hot water system will have an accumulator on the boiler. Also any home that gets its water from a well will have an accumulator. I have an 86 gal. accumulator sitting in the garage.

 

[Tom]

Thanks Don. Reading your message, I now understand. I wasn't thinking of homes heated with water and so couldn't figure out why an accumulator would be required.

 

[Tom]

Thanks for the explanation and drawings Karl. Flipping the position of the tank for different seasons - that's getting way too complex for me.

 

[Karl]

Tom,

Flipping the position of the tank for different seasons - that's getting way too complex for me.

I certainly agree that flipping it is not very practical. I was trying to point out that simply installing one any old way won't necessarily give you the best result. Quoting from the Shurflo manual for their 21 oz. accumulator:

Approximately 15% of the total volume will be stored liquid. Depending on pre-charge pressure to the
accumulator, in relation to the pump turn on/off pressures, stored liquid is about 2 to 4 oz. [60-120 ml]. If
accumulator tank pre-charge exceeds pump turn on pressure, the liquid volume is reduced.

Two to four ounces is a pretty small amount; hardly worth mentioning, and if we apply the same 15% figure to their 6-gallon tank, that comes out to 12.8 to 25.6 oz. [384-768 ml]. Maybe the larger tanks contain the water in the bladder with the charge air surrounding it, but the manual for them was not available online. That would change things dramatically. I'll contact them for additional details and post back.

 

[PancakeBill]

Tom
No need for accumulator with the VSD.  I was going to add one because it worked so well in my previous unit, but liked the VSD.  Cost me more, but space is at a premium in a slide-in, so the VSD made more sense.  Old camoer had a nice access point to install and even then it was a bear to install.  I had the small tank and for our purposes it worked great. 

The new pump has a better flow rate as well, and that made the difference worth it for me.

 

[Tom]

Thanks Bill.

 

[Karl]

Reply from ShurFlo about accumulator tankreceived today; their answers are in red.

Good morning!

As you are well aware, frequent pump cycling in an RV is annoying to say
the least, and many of us are considering installing accumulator tanks.
After reviewing the manual for your 21 oz. unit, several questions have
come up. Perhaps you could answer them.

Re: the 6 gal. tank

1. Is the water contained in the bladder or is that for the charge air? The air is in one side and the water is on the other side. The bladder separate both, so is in contac (sic) with both on its respective side.

2. What is the optimal mounting position? The tank can be mounted in any position it does not have a preference.

3. What is the draw down quantity if mounted with the charge valve on
top? On the bottom? Mounted horizontally? The draw down is the same in any position approximate 1/4 of the volume before the pump turns on.
4. Is there a drain plug for winter storage, and where is it located. The accummulator does not have a valve for winter storage, however the air pressure will expelled all the liquid in the tank. Once the liquid outlet of faucet has been opened.

There is a cautionary note that states that pressure may not exceed 100 p.s.i. or the tank may burst, so a pressure regulator would be a wise choice - even without the accumulator tank.