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Old 22-12-2017, 15:40   #1
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Leakie Marine's Avatar

Join Date: Jun 2014
Location: Melbourne, Australia
Boat: Adams 12, Hick 30
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Parallel water pumps

Hi everyone,
I am rebuilding my plumbing system on my Adams 12. The fresh water pump is getting old and does not supply the water pressure I would like. It is a shurflo 2.8gpm 35psi. I am about to fit an accumulator to help with cycling at low flow rates.

I am thinking of adding another pump in parallel to boost the flow, mainly for the shower. My thoughts are that I can switch it off to reduce usage when cruising away from easily sourced water or have a better flow when in port. It would also give me redundancy at the flick of a switch.

Has anyone got experience with this setup?

I will run the current pump through a 2 minute timer triggered at both the galley and head as sometimes I get air locks and the pump then runs continuously until I notice, this is much more reliable than my memory to turn it off at the board

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Old 22-12-2017, 16:45   #2
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Re: Parallel water pumps

Using parallel pumps might turn out to be more complicated that you think. I would first fix the air leak you have on the suction side of the pump, that's why you get "air locks". That should never happen, something is broken. Don't engineer around the failure--fix it!

Remember, both pumps are only turning on and off by a pressure switch. Especially if they are simple on/off switches they will interact in ways that are difficult to predict.

2.5 gpm at 35 psi should be plenty of water--even for more than one tap open at a time. Why not just fix the pump you have?

All that said... I have a pair of Marco UP2/E pumps in parallel that have variable flow rate pressure controllers and they do behave very well together. It's not often that both come on, but the installed redundancy is an important feature.

If redundancy is really important, you can make SURE you get water out of the tank if you install a manual foot or hand pump as the back up.

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Old 01-01-2018, 16:58   #3
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Location: Melbourne, Australia
Boat: Adams 12, Hick 30
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Re: Parallel water pumps

Thanks Billknny,
Good points, I will be fixing problems as I do a complete re-plumb. I believe the air is getting in at the bladders as the outlet is on top.
Does anyone have any tricks for keeping air out of bladder tanks?
I might have to put another outlet under the bladders or try and reposition them.
I'm glad your setup works well, I will get a new pump and see if it plays well with the old one.
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Old 02-01-2018, 07:39   #4
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Re: Parallel water pumps

If your pump is running, you don't need a new pump. The motor itself is very reliable, it's the rubber that fails. The service kits are very easy to install.
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