Captive Air Tank

[Kimberly Dawn]

I'll add my two cents for what it's worth... I guess that would be $0.02!

When we took possession of our 2019 R27OB, without question the most disturbing feature was the water system. With (4) stations onboard, using anyone was an announcement to all boats around you... think of 11pm in a crowded marina.

I first changed out the OEM Jabsco pump for a 5gpm variable flow Johnson pump that made the system better, but still too noisy. Secondly, I added a Johnson 1.5 liter accumulator immediately downstream of the new pump, and voila, system fixed!

Doing it over, I would add accumulator first for effect. If necessary, I would change out the pump.

Bob
Kimberly Dawn

 

[SJI Sailor]

+1 to Bob, we did the same thing: variable speed pump and small accumulator. Major improvement in noise. (And BTW, besides the other advantages noted we also ended up with a larger, better strainer on the pump.)

 

[Osprey]

The water heaters on our tugs are not vented to the atmosphere. If they were, turning on the water pump would fill the tank to the vent and then continue running thereby pumping water out the vent. This does not happen. Being a closed system, the pump turns off when a preset pressure, about 40 or 50 psi is present in the water heater tank.
Think what happens when we refill the empty heater tank at the start of the season. (Recovery from winterization). With water in the fresh water storage tank we open the hot water tap in the galley and turn on pump. A first air escapes from the tap, then a splutter of air/water and finally straight water. At this point the hot water tank is full with virtually no air at space the top.
Now consider the addition of an accumulator into the water line somewhere after the pump. A good place to locate the accumulator is after the pump but before the heater.
The most common type of accumulator is two chambered. A stretchable membrane separates the two sections. One side is filled with water and the other side (the bladder) has air. Unlike water air is compressible. When the pump is turned on the water pressure compresses the air in the bladder. The pump turns off when the pump’s preset pressure is achiever. When we next open a tap the air in the bladder starts to expand driving water from the water side of the accumulator to the tap. The pump will turn on only after the pressure drops to the pump’s preset “ON” pressure.
The end effect is longer on /off pump cycles and a smother water flow. The total run time of the pump is unchanged. Whatever volume is drawn from the tap has to be replaced with pump operation.

 

[DMD3]

While I don’t have info on the exact design and layout of RT water tank plumbing, reservoirs and holding tanks are most commonly vented to atmosphere… likely through the fill line. Heaters are not. Otherwise a vacuum would be pulled in the tank when the pump is on and distributing water. Check valves prevent what you are describing.

 

[aintmissb]

Osprey, great explanation. Very clear and helpful, thank you!

 

[snydzy]

A video is worth a thousand words….I installed an accumulator tank 6 years ago…and no, it’s not a maintenance item:

https://youtu.be/BkPI-uFlrFA

 

[knotflying]

All I can say is the accumulator tank will avoid the time between the on and off cycle, but will not avoid overall run time of the pump. Hence the annoying sound is spaced longer. Had my boat for 10 years with the same pump. We used water conservatively while anchored and at the dock. We averages 7 gallons of water per day. Also had a compost toilet so no fresh water there either. That can be a whole other long thread discussion. :lol:

 

[BB marine]

I have been following this thread. I have to agree with Mike. Unless you have a large accumulator 5 + gallons it will not reduce the pump use. The small accumulators that are installed in smaller boats help reduce water pulsation. This in many cases does make the water system quieter. It basically stops the plastic water lines from jumping. It also helps "smooth the water flow" It is basically a shock absorber. Many fishing boats use that same pump as wash down pump. Pumping 1000's of gallons of water over the fishing season or seasons. The don't have accumulator tanks! The main reason that many pumps fails, is running dry and the motor gets hot. Or it was just poorly manufactured. I call it the 10% rule. There is about 10% of a manufactures products that are built with marginal specifications. The pumps meet the specs, passes QC, but fail prematurely.

I installed a whole house filter in my C26 and now my Pilot 34. The filter, filters sediment, odor, and some chemicals so the water is drinkable. The other benefit it helps reduce water line hammering. Not has much as a accumulator tank but it was noticeable.

 

[Emerson]

I installed a whole house filter in my C26 and now my Pilot 34. The filter, filters sediment, odor, and some chemicals so the water is drinkable. The other benefit it helps reduce water line hammering. Not has much as a accumulator tank but it was noticeable.

I am contemplating the same but am worried that the reduced flow rate could damage the pump. I wonder if you have thoughts on that. The pump is rated at producing 3.5 gal/minute. The filter I want to use is rated at 1 gal. I am thinking to have two in parallel. I consider the reduced flow a side benefit to stretch the water supply and am okay with it from a consumer perspective. But would I burn up a pump that would struggle to produce a flow that it cannot achieve?


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