Are two accumulators better than one?

[Snackchaser]

Our Oliver came with the Shurflo 24 Oz accumulator that provides a reserve of water so that the pump won’t cycle on when only a small amount of water is needed.  But it never seemed to be quite enough water and the pump would cycle anyway.  It stands to reason that adding a 2nd accumulator would provide twice as much water (48 Oz) before the pump cycled on. . . right?

Being a sucker for projects, I added a 2nd accumulator and there didn’t seem to be any improvement.  In fact, I was surprised to find that there was only 12 Oz of water in reserve between pump cycles.  That was strange, so I removed the second accumulator and tested the original accumulator by itself.  It was only getting 8 Oz of water between pump cycles.  What the heck?  Shouldn’t it be closer to 24 Oz as the accumulators rating implies?

I verified both accumulators had a 30 PSI pre-charge as recommended, and my system seems to have good pressure.  I’ve ordered a water pressure gauge, but I’ve no clue what the accumulator PSI should be in relationship to water pressure.  I’m hoping that the greater wisdom of this forum can provide some insight on this.

Cheers, Geoff

[topgun2]

And here I always thought that the purpose of the accmulator was to even out the pressure in the water line. and had little to do with the amount of water stored in that little tank.

If what I thought is true then that helps explain why you didn't see any marked improvement when you added the second tank.

Bill

[Ollie-Haus]

7 hours ago, Snackchaser said:

Our Oliver came with the Shurflo 24 Oz accumulator that provides a reserve of water so that the pump won’t cycle on when only a small amount of water is needed.  But it never seemed to be quite enough water and the pump would cycle anyway.  It stands to reason that adding a 2nd accumulator would provide twice as much water (48 Oz) before the pump cycled on. . . right?

Being a sucker for projects, I added a 2nd accumulator and there didn’t seem to be any improvement.  In fact, I was surprised to find that there was only 12 Oz of water in reserve between pump cycles.  That was strange, so I removed the second accumulator and tested the original accumulator by itself.  It was only getting 8 Oz of water between pump cycles.  What the heck?  Shouldn’t it be closer to 24 Oz as the accumulators rating implies?

I verified both accumulators had a 30 PSI pre-charge as recommended, and my system seems to have good pressure.  I’ve ordered a water pressure gauge, but I’ve no clue what the accumulator PSI should be in relationship to water pressure.  I’m hoping that the greater wisdom of this forum can provide some insight on this.

Cheers, Geoff

You have them connected in series. They will actually "fight" each other in this configuration and this would actually reduce the effectiveness of the system. They would have to be connected parallel to have a beneficial effect. 

[jd1923]

I tried the same thing, and it didn't work for me. I ended up with a variable speed water pump and the manufacturer specified NOT to use an accumulator. I have 2 on hand if anybody needs one!

[rich.dev]

4 hours ago, Ollie-Haus said:

You have them connected in series. They will actually "fight" each other in this configuration and this would actually reduce the effectiveness of the system. They would have to be connected parallel to have a beneficial effect. 

Good point, but how do you connect them in parallel? I might be wrong but isn't there only 1 input end and 1 output end? 

[Ollie-Haus]

5 hours ago, rich.dev said:

Good point, but how do you connect them in parallel? I might be wrong but isn't there only 1 input end and 1 output end? 

The supply line is fitted with a "T" fitting and feeds each accumulator equally. The discharge from each accumulator connects to the system with the same "T" configuration. Thus each accumulator is supplying equal amount of pressurized water. You now have twice as much water available under pressure from the two accumulators operating equally at the same rate. This of course is limited to the total flow capacity of the water lines supplying and receiving, and both accumulators must be operating equally.

With two accumulators connected in series, the one closest to the demand starts depleting and the second one is only trying to recharge the first one rather than supplying additional water flow to the open tap. It's kind of like several people standing next to each other and trying to pass objects to each other in a chain and filling a box with widgets. If the four people would just individually transfer the items they could from the one container to the other, the rate of transfer would be much faster than if each person has to handle every item being transferred. 

 

Edit: One other thing is the space is very limited so configuring the parallel connection would be the biggest challenge.

On the other hand, what's wrong with the pump coming on when the faucet is opened? What's the difference between 5 seconds till pump kicks on compared to 10 seconds? You have used no extra water in the process and the electrical usage is negligible. Complicating a system for nearly zero gain is kind of pointless. 

Edited March 28 by Ollie-Haus

[Snackchaser]

I got some good comments whether the second accumulator should be in series or parallel, so before I changed the plumbing, I decided to call the Surflo customer service for their opinion.  Their Technician provided a lot of great information, and he confirmed that a 2nd accumulator will provide more reserve water, and it doesn’t matter if it’s in series or parallel.   More interestingly though, he was of belief that one 24 Oz accumulator would only provide 2 to 4 Oz of reserve water.  That sort of answered another question of how much reserve water to expect, and I was happy to know that I was getting more than twice that much.

The technician also recommended that I set the PSI at 2 lbs. less than the pump “turn-on” pressure.  Without knowing exactly what that was, I did some experimentation with higher and lower pressures and found that 30 PSI provides the most reserve water, which was about 13 Oz between pump cycles.   

This is definitely a project where the juice may not be worth the squeeze for everyone.  But for us, it was all about the noise.  That water pump can wake the dead during a late night bathroom visit, or early morning tooth brushing, and any improvement was worth the small effort.  One 24 Oz accumulator wasn’t adequate in this regard, and there’s just not enough room for any of the larger accumulators.

In conclusion, I didn’t get the amount of reserve water I originally expected out of two 24 Oz accumulators, but the improvement was good enough to get a flush and brush without waking the dead.  I’m a happy camper . . . already looking for the next project!

Cheers, Geoff

[SeaDawg]

We still haven't installed an accumulator tank in rhe trailer. My solution to th night time racket is to just turn off the pump, through the night. "If it's yelliw, let it mellow."  Hand sanitizer. Bottle of water.

We had a huge rattle after the (properly sized) accumulator tank in the cabin. (We run off a tank and pump there, too, sometimes. ) We installed a longer line section, with an upward loop in a flexible section, and pretty much solved the problem. Peace and quiet at night.

We chased the noise for a month. It's not fun, and every situation is different. 

Edited April 5 by SeaDawg

[jd1923]

2 hours ago, SeaDawg said:

We still haven't installed an accumulator tank in the trailer. My solution to the nighttime racket is to just turn off the pump, through the night. "If it's yellow, let it mellow." 

We do the same, power off the water pump at night. There's still enough water to flush or even brush teeth. You can also flush the yellow at night w/o water. It empties and generally adds just enough water to seal.

[mossemi]

We turn the water pump off after each use.  Just a habit we developed over time.  With 2 switches, we are never too far away from one.  And under the subject of TMI, we don’t flush yellow at night, we accumulate and flush in the morning.  We also turn off the city water supply when we leave the campground.

Mossey

[dewdev]

If you all had a compost toilet, you would not need the water pump on at all for flushing.

Just making a little light of the subject. Ha Ha

[topgun2]

1 hour ago, dewdev said:

If you all had a compost toilet, you would not need the water pump on at all for flushing.

Sure - but - 

its still fun to just sit there and count all that money I saved.  🤑

Ha Ha.

[jd1923]

Much rather flush than compost! Yuck, just drain the black once a week!

[Jason Foster]

Flushing the yellow wouldn't work for me but it would for my wife.