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Old 06-05-2017, 03:36   #1
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Shower drain vented loop

The plumbing drain line for the shower on Shiva was rub entirely below the water line to a sea cock below the galley sink. I kept it closed except when using the shower. The other day when trying to explain this to the wife it occurred to me that i should add a vented loop to prevent siphoning and water being pulled back into boat...

Is there a down side to this?

Thanks for your replies.
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Old 06-05-2017, 06:24   #2
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Re: Shower drain vented loop

Personally, I opted to run my shower drain direct to it's own bilge compartment and it's pumped overboard. No more valve turning, smell, or worrying about SeaWater coming into the boat if I forget the valve.
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Old 06-05-2017, 06:44   #3
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Re: Shower drain vented loop

Quote:
Originally Posted by Sandero View Post
The plumbing drain line for the shower on Shiva was rub entirely below the water line to a sea cock below the galley sink. I kept it closed except when using the shower. The other day when trying to explain this to the wife it occurred to me that i should add a vented loop to prevent siphoning and water being pulled back into boat...



Is there a down side to this?



Thanks for your replies.

I don't see any point to a vented loop for this application. If the shower is below the water line it would never drain completely.
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Old 06-05-2017, 06:47   #4
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Re: Shower drain vented loop

yes it does.... it is PUMPED OUT...

The issue is that with the sea cock OPEN it is possible for the seawater to flow BACK thru the pump and into the shower pan. Will a loop the sea water will not flow back.

But will the pump cause the vent to leak????
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Old 06-05-2017, 07:53   #5
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Re: Shower drain vented loop

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yes it does.... it is PUMPED OUT...

The issue is that with the sea cock OPEN it is possible for the seawater to flow BACK thru the pump and into the shower pan. Will a loop the sea water will not flow back.

But will the pump cause the vent to leak????
No. As long as the pump is before the loop but you will have a certain amount of water draining back when the pump shuts off. Check valves on shower sump lines always seem to get clogged.
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Old 06-05-2017, 08:17   #6
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Re: Shower drain vented loop

I installed a shower grate in the head and ran a drain to a "Rule Drain Box" (800 gph) which was mounted in the bilge. Then a 1/4 inch exit hose was run from the Rule Drain Box above the water line to a vented loop and then back below the water line to a dedicated thru-hull fitting. Works great and the Rule Drain Box is only a $140.00 item so I get a spare onboard that is easy to swap out.
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Old 06-05-2017, 08:43   #7
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Re: Shower drain vented loop

About three years ago, I replaced my custom drain box with the Whale Intelligent control (IC) system (to whom I have no connection). I teed the shower drain and the reefer drain to the suction of a small positive-displacement pump, and installed a sensor there. When either drain has water, the pump runs to empty both lines; it has a high loop in its discharge to prevent backflow. There is no slimy box to clean, and it's worked smoothly for two years.
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Old 06-05-2017, 09:07   #8
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Re: Shower drain vented loop

my shower has a sump with a lovely automatic bilge pump err sump pump for emptying into the forward bilge emptying system-- both forward pump and sump use the same exit hosing. works fine.
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Old 06-05-2017, 10:33   #9
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Re: Shower drain vented loop

I plumbed my shower sump, which is below the water line into the sink, which is above the water line with a T, just below the bowl, this is in effect a vented lupe.
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Old 06-05-2017, 11:39   #10
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Re: Shower drain vented loop

If you shower drain is below the water line the best rig is drain to a sump in the bilge which can be pumped out. That avoids any need to pump the shower dry, the anti siphon loop should be used with your pump. In the event of pump failure overflows go harmlessly to the bilge.
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Old 06-05-2017, 14:30   #11
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Re: Shower drain vented loop

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Originally Posted by Michael Baker View Post
I installed a shower grate in the head and ran a drain to a "Rule Drain Box" (800 gph) which was mounted in the bilge. Then a 1/4 inch exit hose was run from the Rule Drain Box above the water line to a vented loop and then back below the water line to a dedicated thru-hull fitting. Works great and the Rule Drain Box is only a $140.00 item so I get a spare onboard that is easy to swap out.
ouch, $100 wasted on 'rule's box'. I just installed a $40 sump box, works great.
https://www.amazon.com/Amarine-made-...ds=shower+sump

As for the vented loop, yes, that will prevent back flow and risk of sinking the boat. No issue with it working with the pump. It will leave the amount of water in the hose up to the top of the loop inside the boat. It will stink if you don't have a sump box or maybe an ounce of bleach at the end of the shower would work?
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Old 06-05-2017, 14:43   #12
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Re: Shower drain vented loop

Thanks for the replies. My bilge is dry so I don't want to have water in it. I'll use a vented loop. The shower pump is plumbed to a T which can be switched over to a bilge pump for the virtually always dry main bilge.

I like the chlorox idea!
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Old 08-05-2017, 08:54   #13
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Re: Shower drain vented loop

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Originally Posted by zstine View Post
ouch, $100 wasted on 'rule's box'. I just installed a $40 sump box, works great.
https://www.amazon.com/Amarine-made-...ds=shower+sump

As for the vented loop, yes, that will prevent back flow and risk of sinking the boat. No issue with it working with the pump. It will leave the amount of water in the hose up to the top of the loop inside the boat. It will stink if you don't have a sump box or maybe an ounce of bleach at the end of the shower would work?
The Rule pumps 800 gph so has better lift to the vented loop, this prevents drain water falling back into the drain box that again triggers the float switch in an endless game of pump and return......
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Old 08-05-2017, 10:02   #14
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Re: Shower drain vented loop

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The Rule pumps 800 gph so has better lift to the vented loop, this prevents drain water falling back into the drain box that again triggers the float switch in an endless game of pump and return......
What stops the water from draining back is the non-return valve. The vented loop stops a siphon from flooding the boat.
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