Bilge hose - important difference!

Fr. Frank · #1 02-06-2008, 08:28 AM

A friend and I did a test last night on the difference between corrugated plastic bilge hose, and smooth-wall hose. The results were surprising to me.

Using a 600 gallon steel stock tank, and a 325 gallon clear sprayer tank with exterior volume markings, we measured the output and amperage draw of two bilge pumps using the different hoses. We placed the pumps in the bottom of the stock tank, and then hooked the pumps up to a battery for 15 minutes.

My friend then had a beer (one during each test). I had a diet Dr. Pepper. (one for all 4 tests)

The first pump used was a new Attwood 500gph automatic bilge pump from WalMart. Using a 6' long piece of straight wall 3/4" garden hose, after 15 minutes the measured output was approximately 180 gallons, or about 620 gallons per hour. The amperage draw throughout was about 1.9-2.0 amps.

Repeating the process with 5' of corrugated 3/4" bilge hose gave us an output of approximately 95 gallons, or 380 gallons per hour, with an amperage draw of 2.2 amps.

The next pump we used was a 2 yr. old Rule 1250 manually switched pump, with a 1 1/8" output. Using 5' of fiber-reinforced straight-wall bilge hose, we got an output after 15 minutes of about 320 gallons, or 1280 gallons per hour, at 2.7 amps

Using 5' of corrugated bilge hose from West Marine, we got an output of only 240 gallons, or 960 gph, at 2.9 amps.

People, the difference may be between sinking and floating. These pumps are obviously rated for using straight-wall hose, NOT corrugated hose. Using corrugated hose provides less output while using more electricity.

While I expected a slight difference, I didn't expect so dramatic a difference. And I have corrugated hose hooked up to all three of my pumps in my bilge.

(Yes, I have THREE bilge pumps in a 20' Seafari, all 1200 gph rated. Two at the transom, and one in the bow under the cabin. I discovered the hard way that with 5 persons on board, and three of them sunning on the cabin deck, a Seafari will begin to sink bow-first when the drain plug is left in the engine well instead of being stuck in the little hole in the transom)

76Red18 · #2 02-06-2008, 06:32 PM

That is suprising. I had kink problems with smooth hose so I used the kind from West Marine that has the black spiral band around it (almost smooth on the inside but hard to clamp) for the 3 pumps on my 18'er; 2 1500s and a 750 auto all on seperate batteries.

cSickNick · #3 02-06-2008, 07:27 PM

Quote:

Using a 6' long piece of straight wall 3/4" garden hose, after 15 minutes the measured output was approximately 180 gallons, or about 620 gallons per hour.

Minor math correction 180 x 4 = 720 GPH. Just wanted you to know i was paying attention.

Interesting results, but the real question is "how long did your battery last before the young ladies sunning in bikini's got wet??"

- Nick

eggsuckindog · #4 02-07-2008, 02:11 AM

The issue I've had is the wire reinforced hose will not hold when clamped and will come off, at 1 1/8" seacock fills the boat quick.

Fr. Frank · #5 02-07-2008, 08:50 AM

For the test. I used the 1 1/8" hose that has threads running through them, but not wire. After the test I used that piece to replace the corrugated hose on one of my pumps

McGillicuddy · #6 02-07-2008, 02:02 PM

Wow. Thanks! That is truly valuable research, not sure what hoses I have on the Seafari (still rewiring) but that will be definitely addressed. I would have never guessed the the difference to be so significant. Fantastic info. Send that to Mythbusters...

ps. what kind of mileage did you end up with on the 90 Optimax?

Fr. Frank · #7 02-07-2008, 02:29 PM

Unable to get my navman working. My estimate is about 5.3 to 5.5 gph at 23-24 mph, or about 4.5 mpg. I ran for one full hour (timed) on a 6 gal. portable tank, and still had about 1/2 to 2/3 of a gallon left.

Fishjack · #8 02-08-2008, 02:15 AM

What I cannot believe is that they actually advertise that black corrugated hose at "bilge hose"... Not only does it restrict flow but when I tried using it I had to replace it once a year because it would get brittle and crack/break in the heat.

From experience - bilge pumping water out under top cap onto deck is not good...

Islandtrader · #9 02-08-2008, 09:17 AM

I do believe, we have our own "Myth Buster" here on CSC. How cool is that.

spareparts · #10 02-08-2008, 09:10 PM

several years ago there was an article in some boating magazine that tested bilge pumps and hoses like ya'll did. They pointed out that bilge pumps are rated at 14.5 volts(max rating) with no hose attached, The numbers ya'll gave are pretty good considering how the manufactures rate them. I have been using the black 1 1/8 smooth wall coil reinforced bilge hose. I find that heating the hose with a heat gun allows me to get the hose all the way up on the nipple, then clamping it while its still warm usually secures it and makes a leak proof connection, I have in the past had to put a little sealant on a couple when using old hose to help seal it. BTW, I have three 2500 gph pumps in my 20 ft boat. I have replaced way too many new pumps to rely on just one back up. A good experiment is to back your boat in with out the plug(don't take it off the trailer) and see if your pump can keep up with the water coming in that small hole, its very supprising.