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Fresh water pump question

5K views 21 replies 12 participants last post by  billyruffn 
#1 ·
Right now I have a 3gpm PAR belt driven fresh water pump, I want to install a 4.5-5 gpm pump to reduce the pulsation and increase output from the showerhead, is there a side effect I should be aware of ??, all lines are in good shape
 
#2 ·
Do you have an expansion tank in your system? If not adding one of these should get rid of the pulsing. The expansion tank has an air bladder and stores a quanity of water at your systems pressure and will reduce pump cycles and the pulsing. If you have an expansion tank the bladder inside it may be flooded or the tank needs pumped up with air. You can also make sure your showerhead is a reduced flow model.

Good luck,
 
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#3 ·
That's an excellent idea. If you are happy with the flow rate, the expansion tank is a better solution and is easily maintained. We have an expansion tank in our gas furnace/hot water radiator house heating system. Occasionally we get "water hammer" and we simply go to the highest rad in the house and bleed off trapped air which is giving the system a fit of the wobblies.

Here's a brief explanation of the principles. The tank needed for a boat's plumbing could be quite compact.

http://en.wikipedia.org/wiki/Expansion_tank
 
#4 ·
Expansion tanks are often installed to stop water hammer, said the plumber's son.
 
#6 ·
One thing that bit me in the wallet was my replacement of a struggling PAR belt driven pump was that I was un-aware of the Max PSI that my hot water heater pressure release valve was spec-ed for. I installed a Very High Pressure 51 PSI I think water pump last spring not knowing that my hot water heater said to only use up to 48 PSI. I didn't find that out until this fall reading up on my hot water heater to look at pressure valve replacement :eek: It worked fine for a while - although it was really too much pressure (splashing water in the sink) - then mid-summer the hot water heater pressure release valve started its own form of Hammering..... and I mean Hammering :eek: :eek: when the drain hose that was connected to it would jump around with the on and off release of pressure. Just last week I re- replaced it with a 40 PSI pump and I HOPE that when I reconnect the hot water heater in the spring that the relief valve will be happy :rolleyes:
Probably a rare issue but it took me by surprize so it seemed worth mentioning :)
 
#7 ·
Poopdeckpappy,

My gut feeling on this is that the higher pressure/volume pump will not solve the pulsing (might make it worse). Normally the problem you are having is addressed by adding the "expansion" tank mentioned above.

If you are having trouble locating an "expansion" tank, I thought I'd mention that in marine applications they are generally referred to as "accumulator" tanks. They are a fairly common component of domestic fresh water systems aboard sail and powerboats.
 
#9 ·
Poopdeckpappy,

My gut feeling on this is that the higher pressure/volume pump will not solve the pulsing (might make it worse). Normally the problem you are having is addressed by adding the "expansion" tank mentioned above.
Just to be clear - my post about my high pressure pump wasn't meant as a cure for your pulsing or mine as I have an accumulator tank. My pump either needed rebuilding or replaceing and I chose replaceing. I just wanted to share my self-generated problem in case someone does need or wants to replace a pump with something other than the one that came with the boat.
 
#8 · (Edited)
PDP,
I have a Jabsco 1 litre accumulator tank on my fresh water system and have good steady pressure, and no pulsation at all. Install is easy, if you have 1/2" water hose. You just have to find a good spot on the high pressure side of the pump and cut the hose. The two cut ends go on the hose barbs and the third point of the "T" is the tank itself.

Defender looks to have the best price on it too, but you should shop around first.
http://www.defender.com/category.jsp?path=-1|51|299222|121271&id=316442

Here is a pic of the Jabsco 1quart, 1 litre, and 2 gallon accumulators
 
#11 ·
This is great stuff, thanks for the replies and leads on accumulator tanks, it isn't as simple as I thought, the water heater issue was good to know too, Thanks Stan, I would have never thought of that.

I thought that being that I pump FROM the tank and TO the fixtures, simply increase volume drawn would increase the volume out ( I hoped ).
 
#13 · (Edited)
This is great stuff, thanks for the replies and leads on accumulator tanks, it isn't as simple as I thought.....
I think it's more simple than you thought. An accumulator tank costs under $50. It takes about 15 min., a sharp blade, a few hose clamps, and the right place to mount. The accumulator draws no power, and it's (cough cough) "maint. free".

Buying a bigger pump would have been harder and costlier.

Here is a pic I found of typical install diagram

 
#14 ·
A larger accumulator has more capacity to keep pressure on the system, it will keep the fresh water pump cycles down. However, to pump the system back up to normal pressure the pump may run a little longer when it does come on. If you get a bigger accumulator you may just need that bigger pump after all if you don't want the pump running for a whole minute just to get the system back up to pressure.

You may prefer stainless to plastic accumulator (or the other way around). Space to install a larger tank may be a consideration too. Cost considerations come with quality and material (as always). There are a few manufactures out there also: shurflo, jabsco, grocco, and a few others.

My system is small and simple, I only need a small accumulator, a small pump, and a small water heater. If you have an elaborate system or maybe a few people using it at the same time (washing dishes while you shower), you may need bigger components.
 
#16 ·
You might want to look into using a variable speed pump that operates with a pressure sensor to control pump output based on how much water is being demanded (Jabsco and Shurflo make them). They're a bit more expensive (about $75-100 more) but they eliminate the need for the accumulator tank. You do have to be careful of water consumption, however, as they can operate at fairly high pressures. I installed one several years ago when I got a water filter/purifier (Sea Gull IV) that required more pressure than the old PAR (with an accumulator tank) would put out. I've had both Shurflo and Jabsco pumps on the boat -- the Shurflo Smart Sensor was replaced twice (on warranty) and I now have a Jabsco that works well. One disadvantage (aside from price) is that they are fairly quiet -- if you spring a leak somewhere, as we did once, you can end up with a bilge full of fresh water pretty quickly. Shurflo has a modification you can install that will light an LED when the pump is operating.
 
#17 ·
One thing to note: Do not use copper or other rigid (pvc etc) to connect... use the clear tubing as they absorb more of the impact and will not strain as much under pressure (and its cheaper too)....clear is great because you can determine by looking when the tubing is failing or if the water is getting too dirty etc...
 
#18 ·
For someone like Christyleigh who had too much pressure, you can get pressure regulators to lower the system pressure before any devices such as the hot water tank. In this case I would put the accumulator tank (thanks JohnRPollard) after the pump but before the pressure regulator maintaining a reserve of higher pressure water. These are passive spring loaded devices.

I thought I would mention it because it could save somebody else from buying a new pump. I paid about $30 for one at a supply house not too long ago.
 
#19 ·
You really want to make sure that you've got a small accumulator tank in the system, since that will do far more to reducing the pump short-cycling. :) The larger the accumulator tank, the more even the water pressure will be and the more able the system will be to handle high-demand loads.
 
#22 ·
Xort,

I also have a short piece of clear tube between the fresh water pump and the pvc quick connect water pipe that runs throughout the boat. I have done as you suggested and wrapped the 18" length with black duck tape to keep the light out. I have a strainer between the tanks and the pump that has a clear plastic cover. I find that this lets me see what's going on with the water -- when the fine mesh strainer gets full of goo, it's time to flush the tanks. When it starts getting clogged with bits of rust and paint chips, it's time to get out the chipping hammer, and sand paper and paint the inside of the steel tanks.
 
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