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Old 03-03-2016, 21:04   #1
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Backflow Valve in Bilge Pump Drain - Good Idea?

I have a Rule, Model 24, 360 GPH bilge pump, with a 3/4" exit tube that I connected to a brass backflow valve using a two inch length of garden hose. The other end of the backflow valve is connected to a 1" drain hose which leads to a through hole above the waterline - perhaps two feet above the pump.

I recently replaced the pump, and reading the instructions, I noticed that they seemed to suggest that there should be no backflow valve in the line. Does anyone know why this is, and if having the valve in the drain line could cause me problems.

Also, the seems to be clogging rather frequently, but I will address that issue in a separate post.

Thanks to all for your help.

G2L
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Old 03-03-2016, 21:15   #2
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Re: Backflow Valve in Bilge Pump Drain - Good Idea?

That's why it's preferable not to have a backflow prevention device on the bilge pump system. They clog easy.
You can build a strum box around the hose end, and try to prevent crap from getting to the hose end and to the backflow preventer.

That or learn to live with a wet bilge.
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Old 03-03-2016, 21:34   #3
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Re: Backflow Valve in Bilge Pump Drain - Good Idea?

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Originally Posted by Strait Shooter View Post
That's why it's preferable not to have a backflow prevention device on the bilge pump system. They clog easy.
You can build a strum box around the hose end, and try to prevent crap from getting to the hose end and to the backflow preventer.

That or learn to live with a wet bilge.
I did get a blockage, but it seemed to be in a loop that goes over a beam in the superstructure before exiting the boat. I am going to edit my original post to make the set up clearer to folks.

Thanks,

G2L
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Old 03-03-2016, 21:37   #4
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Clarification of the pump arrangement

Quote:
Originally Posted by Gone2long View Post
I have a Rule, Model 24, 360 GPH bilge pump, with a 3/4" exit tube that I connected to a brass backflow valve using a two inch length of garden hose. The other end of the backflow valve is connected to a 1" drain hose which leads to a through hole above the waterline - perhaps two feet above the pump.

I recently replaced the pump, and reading the instructions, I noticed that they seemed to suggest that there should be no backflow valve in the line. Does anyone know why this is, and if having the valve in the drain line could cause me problems.

Also, the seems to be clogging rather frequently, but I will address that issue in a separate post.

Thanks to all for your help.

G2L
Wanted to add that, before the drain line goes up to the through hole, it must cross over a 6" beam in the hull which supports the port side engine mounts. See my soon-to-be thread on the clogged line, entitled "Shrimp Fry Clogging my Bilge Drain????"
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Old 03-03-2016, 22:57   #5
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Re: Backflow Valve in Bilge Pump Drain - Good Idea?

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Originally Posted by Gone2long View Post
I have a Rule, Model 24, 360 GPH bilge pump, with a 3/4" exit tube that I connected to a brass backflow valve ...
seems to be clogging rather frequently...
Such an installation is unreliable and prone to frequent blockages.

NEVER install a check valve in a bilge pump line.
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Old 03-03-2016, 23:46   #6
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Re: Backflow Valve in Bilge Pump Drain - Good Idea?

Besides clogging, a check valve or back flow preventer reduces the flow by 20-40%.
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Old 04-03-2016, 00:11   #7
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Re: Backflow Valve in Bilge Pump Drain - Good Idea?

Depending on where you have the check valve(backflow valve) it may prevent the pump from priming and this rather than blockages might be the reason it does not always work. It's better if the water remaining in the line drains completely back into the bilge to ensure there are no airlocks trapped in it when the pump restarts. Run a loop all the way up under the deck and remove the backflow valve and see if that fixes your problem.
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Old 04-03-2016, 04:26   #8
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Re: Backflow Valve in Bilge Pump Drain - Good Idea?

The easy solution to this is multiple pumps. I have a Whale Supersub as a maintenance pump. It came standard with a check valve. It has a decent strainer and has not clogged so far.

For shifting water - which is a different job, requiring a different tool, than keeping the bilge dry --, I have a pair of the large Rule 4000s. No check valves for all the reasons stated above.

Nothing wrong with a check valve provided it's not in the main pump.

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Old 04-03-2016, 06:12   #9
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Re: Backflow Valve in Bilge Pump Drain - Good Idea?

Quote:
Originally Posted by Gone2long View Post
I have a Rule, Model 24, 360 GPH bilge pump, with a 3/4" exit tube that I connected to a brass backflow valve using a two inch length of garden hose. The other end of the backflow valve is connected to a 1" drain hose which leads to a through hole above the waterline - perhaps two feet above the pump.

I recently replaced the pump, and reading the instructions, I noticed that they seemed to suggest that there should be no backflow valve in the line. Does anyone know why this is, and if having the valve in the drain line could cause me problems.

Also, the seems to be clogging rather frequently, but I will address that issue in a separate post.

Thanks to all for your help.

G2L
No check valve in the bilge pump discharge hose, no garden hose and no "brass" in anything that involves seawater.

Get rid of the check valve and garden hose and do it right.
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Old 04-03-2016, 09:08   #10
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Re: Backflow Valve in Bilge Pump Drain - Good Idea?

Ditto on the removal of the check valve. But try switching to smooth wall hose. All the coreggations in the standard bilge hose slows down the flow, and can fill with debris. That tip came from a guy that builds boats for a living, and worked for me.
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Old 04-03-2016, 09:13   #11
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Re: Backflow Valve in Bilge Pump Drain - Good Idea?

I was thinking of adding a small extra pump just for the last inch or so that would be on a separate on demand when I wanted to fully dry out that last annoying bit without leaning stretching way down with a sponge.
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Old 04-03-2016, 09:41   #12
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Re: Backflow Valve in Bilge Pump Drain - Good Idea?

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Originally Posted by Terra Nova View Post
Such an installation is unreliable and prone to frequent blockages.

NEVER install a check valve in a bilge pump line.
ESPECIALLY if you never intend to service them.
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Old 04-03-2016, 09:43   #13
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Re: Backflow Valve in Bilge Pump Drain - Good Idea?

seems like there is a balance here between whether you really wish to keep yr bilge as dry as poss, or just let the water run back down from the pump into the bilge when the pump stops. This was happening to me when i replaced the float switch so that approx every 45 secs the bilge pump would pump for about 3 seconds. Fixed it with a non-return valve at bottom of the hose but my bilge is usually v clean has 6" high mesh walling around top edge of the bilge so the crud never gets down there.

OK, so if i find that the non-return valve gets blocked i can take it out and raise the float switch a couple of inches so the returning water does not set it off again. So far hv not had to do this and I have an almost dry bilge.
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Old 04-03-2016, 10:20   #14
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Re: Backflow Valve in Bilge Pump Drain - Good Idea?

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Originally Posted by SaltyMetals View Post
seems like there is a balance here between whether you really wish to keep yr bilge as dry as poss, or just let the water run back down from the pump into the bilge when the pump stops. This was happening to me when i replaced the float switch so that approx every 45 secs the bilge pump would pump for about 3 seconds. Fixed it with a non-return valve at bottom of the hose but my bilge is usually v clean has 6" high mesh walling around top edge of the bilge so the crud never gets down there.

OK, so if i find that the non-return valve gets blocked i can take it out and raise the float switch a couple of inches so the returning water does not set it off again. So far hv not had to do this and I have an almost dry bilge.
+1 Exactly.
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Old 04-03-2016, 10:43   #15
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Re: Backflow Valve in Bilge Pump Drain - Good Idea?

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.............OK, so if i find that the non-return valve gets blocked i can take it out and raise the float switch a couple of inches so the returning water does not set it off again. So far hv not had to do this and I have an almost dry bilge.
It's not "if" the check valve gets blocked, it's "when" the check valve gets blocked.

The valve could get blocked in the open position, in which case, it's no longer a valve, it's just a restriction.

If it gets blocked in the closed position, you will have a pump that runs but does not empty the bilge. This could happen at an inopportune time like when you have a leak from the engine or potable water system or when you have a hole in the hull.

The best practice is to have no check valve in the bilge pump plumbing and to have the output hose as short and direct as possible.
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