The Great Bilge Pump Debate, 2023 Edition

[Kings Gambit]

Sooooo, let us twist the topic a little.

In my mind, there is a far better chance of my boat having a minor leak the a major catastrophic failure.
My bilge pump is a rule 1500, 1500 gph or 25 gpm.
So lets do some math. Kind of a nerdy thing but it is Monday and I am bored.
PS, the numbers are approximate.

Let's look at the maximum flow rate through various size pipes with the assumed leak being low pressure, about 6 f/s flow velocity.
1/2"........... 7 gpm or 420 gph
3/4"........... 11 gpm or 660 gph
1" .............. 16 gpm or 960 gph
1 1/4" ........ 25 gpm or 1500 gph
It is at this point the secondary pump kicks in. Mind you the secondary pump has to be mounted in a manner to keep the primary pump motor dry. It is my opinion that the secondary pump needs to be larger than the primary pump.
1 1/2" ........ 35 gpm or 2100 gph
2" ............... 55 gpm or 3300 gph

Let's up the game and assumed average pressure is 20-100 PSI. About 12 f/s flow velocity.
1/2"........... 14 gpm or 840 gph
3/4"........... 23 gpm or 1410 gph
Again, at is at this point the secondary pump kicks in.
1" .............. 37 gpm or 2,200 gph
1 1/4" ........ 62 gpm or 3750 gph

It is my best guess, good pumps and a good battery with a charger should keep my boat high and dry.

In my opinion, unless you measure the overboard pump rate on your boat you do not know and cannot usefully estimate your dewatering rate. Also, the flow rate into the boat as a measure of pipe ID is affected by the depth of the hole.

So if bored go down to your boat and flood the bilge using the dock hose, get the pumps working, adjust the faucet output to match bilge output to keep bilge water level steady, then measure the bilge pump out rate. All need you for that is one liter graduated cylinder in milliliters and a stop watch. I think you will be lucky to see half the GPH’s you’re figuring on. I was surprised.

 

[SycloneDriver]

In my opinion, unless you measure the overboard pump rate on your boat you do not know and cannot usefully estimate your dewatering rate. Also, the flow rate into the boat as a measure of pipe ID is affected by the depth of the hole.

So if bored go down to your boat and flood the bile using the dock hose, get the pumps working, adjust the faucet output to match bilge output to keep bilge water level steady, then measure the bilge pump out rate. All need you for that is a graduated cylinder in milliliters, and a stop watch. I think you will be lucky to see half the GPH’s you’re figuring on. I was surprised.

I was actually planning do something exactly like that in a few hours.

 

[capta]

Since the day I began sailing boats with more than 1 battery, the 1-2-off switch was; 1= house battery, 2= engine battery and obviously off is as stated.
I think it is a great idea to have at least one's major bilge pump directly off the battery, after a fuse or circuit breaker. It makes absolutely no sense to me to have the main panel on when one is off the boat as, if there is a voltage leak, it could deplete the battery before the pump is needed.

 

[SycloneDriver]

So I timed my bilge pump rate. One bucket in 20 to 24 seconds. Bucket appears to be about 2 gallons.

Looks like 6 gallons per minute to me. I tried it twice, once with the battey charger on and once with it off. The battery was full and the times were about the same.

 

[Ralph Johnstone]

Looks like 6 gallons per minute to me.

Did you mention the make and model of your pump somewhere in this post ? I'm blind in one eye and can't see out of the other.

 

[SycloneDriver]

Did you mention the make and model of your pump somewhere in this post ? I'm blind in one eye and can't see out of the other.

It's in the attachment (picture).

 

[Tally Ho]

It's in the attachment (picture).

So that is a diaphragm pump?

Johnson Viking Power 16 Waste Water Pump - 10-13350-03

Features : Compact shower drain, bilge and waste water pump Specifically designed to pump waste water, the Viking Power 16 is an ultra-modern, single-chamber self-priming diaphragm pump that can be set up in several different pump/motor configura

defender.com

If it is this one, it says capacity is 4.5 gal/minute open flow.

Greg

 

[SycloneDriver]

So that is a diaphragm pump?

Johnson Viking Power 16 Waste Water Pump - 10-13350-03

Features : Compact shower drain, bilge and waste water pump Specifically designed to pump waste water, the Viking Power 16 is an ultra-modern, single-chamber self-priming diaphragm pump that can be set up in several different pump/motor configura

defender.com

If it is this one, it says capacity is 4.5 gal/minute open flow.

Greg

Yes, it's a diaphragm pump.

The label says 4 us gallons at 1 meter. Sounds about right to me.

I think my bucket is closer to 1.75 gallons. So I measured about 5.25gpm at 12.9 volts. That's 315gph or almost as much water as my hot tub holds, it take some time to fill it with a garden hose too.

Will it keep my boat from sinking? Yes, but only if the in flow of water is less than the pump can remove. Simple right.