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Old 29-07-2013, 12:34   #1
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Raw water pump. You can't get there from here

So in the course of installing new hoses for the raw water system, overhauling the strainer and installing a new water pump">raw water pump I have run into a road block.

The original strainer is a large Groco with 1" NPT female sockets on the strainer body. The Sherwood water pump has 1/2" NPT female sockets on the pump. So far I have not found a way to get from 1" to 1/2".

Groco sells elbows that are 1" NPT male with 1 1/8" or a 1 1/4" hose barb. I can get a 1/2" NPT elbow for the pump with 3/4" hose barb. Of course the ideal would be a step down fitting on the strainer that would take the 1" NPT out to a 3/4" hose barb. I cannot find such a think in bronze and don't want to go with brass.

Plan B would be a step down double ended hose barb but again I cannot find this in bronze.

So my options so far are

1. Buy a new strainer with 1/2" NPT fittings. Much smaller than the old strainer but big enough? Groco rep thinks the old strainer with 1" fittings is way overkill for a 60 HP sailboat diesel. Would save a little room in the engine space as well.

2. Stack up 2-3 brass fittings to get from the 1" NPT down to the 3/4" hose. I don't like no stinkin' brass in my raw water system.

3. Go to Home Depot and get a plastic (nylon, ABS, PVC, ?) step down hose barb. This is on the cold side of the raw water system.

OR - does anyone know where I can get a hose fitting to step down from 1 1 1/4" ID hose to 3/4" ID hose?

Thanks
Skip
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Old 29-07-2013, 12:59   #2
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Re: Raw water pump. You can't get there from here

Marine & Boat Supplies Since 1928 | Fisheries Supply

I didn't see a listing for what you wanted in reducers at this site but a phone call might connect you with someone who knows a good source in bronze. They've always been helpful for me.
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Old 29-07-2013, 13:23   #3
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Re: Raw water pump. You can't get there from here

You can get pretty much any size bushings you need from either McMaster-Carr or Grainger. Let me know if Grainger gives you a hard time about order because you don't have a business account.
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Old 29-07-2013, 13:27   #4
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Re: Raw water pump. You can't get there from here

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Originally Posted by JK n Smitty View Post
You can get pretty much any size bushings you need from either McMaster-Carr or Grainger. Let me know if Grainger gives you a hard time about order because you don't have a business account.
Already looked at both and maybe I'm missing something, but found only brass. I am afraid of mixing brass in the system. Would rather go with nylon or PVC
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Old 29-07-2013, 13:34   #5
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Re: Raw water pump. You can't get there from here

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Originally Posted by skipmac View Post
The original strainer is a large Groco with 1" NPT female sockets on the strainer body. The Sherwood water pump has 1/2" NPT female sockets on the pump. So far I have not found a way to get from 1" to 1/2".

So my options so far are

1. Buy a new strainer with 1/2" NPT fittings. Much smaller than the old strainer but big enough? Groco rep thinks the old strainer with 1" fittings is way overkill for a 60 HP sailboat diesel. Would save a little room in the engine space as well.

If the new Sherwood pump will only take 1/2" worth of water flow input -- so to speak -- I'd think a 1" strainer would really only function at the constricted 1/2" throughput rate. If so, a smaller strainer with 1/2" outie would seem to be an OK option. Perhaps you can cross-reference against engine data to be sure the strainer/pump output would be sufficient...

-Chris
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Old 29-07-2013, 16:34   #6
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Re: Raw water pump. You can't get there from here

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Originally Posted by ranger42c View Post
If the new Sherwood pump will only take 1/2" worth of water flow input -- so to speak -- I'd think a 1" strainer would really only function at the constricted 1/2" throughput rate. If so, a smaller strainer with 1/2" outie would seem to be an OK option. Perhaps you can cross-reference against engine data to be sure the strainer/pump output would be sufficient...

-Chris
Since the new pump is identical to the old then the pump capacity must be right. And, as you point out, the 1" strainer outlet is constrained buy the 1/2" pump inlet, but that doesn't address the capacity of the strainer system itself which I don't think is really a constraint on the system, so thinking about this option.
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Old 29-07-2013, 16:48   #7
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Re: Raw water pump. You can't get there from here

A brass bush or two should be fine with the bronze strainer. I have a 1-1/2" strainer bushed down to 1/2". As there will be a hose coupling and hose on the end the brass is not under structural loading. If your really worried about it, just change out the brass every 5 years or so and you'll be fine. Over time the zinc in the brass will be sacrificed. But it should be fine in a non-structural area. That assumes that everything else is brass or bronze in the inlet The remaining copper in the brass will still be stronger then nylon anyway.
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Old 29-07-2013, 16:49   #8
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Re: Raw water pump. You can't get there from here

I've seen reducing barbs fom 3/4 pipe all the way to 3/8" barb. Not sure about 1". Not positive they were bronze or not. Personally I'd go brass before plastic. Easy to keep an eye on, and it's just water that's not in the electrolysis stream much.. (unless your strainer is bonded) I've seen every type of plastic; grey, white, black, nylon, schedule 80 fail in service from vibration etc. You're betting your boat on that fitting.... if worried you could put a zinc in the strainer.... I guess SailorChic and I are pragmatists!
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Old 29-07-2013, 17:01   #9
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Re: Raw water pump. You can't get there from here

Plus with that plumbing engineering background (among other things), I know the strength of materials pretty well. Yes Brass is a no no with through hulls and anything under structural loading, But a bush in a fitting is not under that much loading when the next fitting is a hose barb and flex hose.

I have Brass on mine too, Go 1x3/4 on Bush and then just get a 3/'4 by 1/2 brass hose barb. Easy. Put teflon tape on the threads and make it tight. It will be fine.
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Old 29-07-2013, 17:41   #10
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Re: Raw water pump. You can't get there from here

Well the plastic was option #3 on my list but brass does make me nervous on a boat. With the two smartest members of the forum telling me it's OK then what can I say.

Brass fittings it is, but if my boat sinks in the middle of the ocean I'm coming back to haunt both of you.
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Old 29-07-2013, 18:04   #11
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Re: Raw water pump. You can't get there from here

I have plastic male thread to barb fittings on the GROCO raw water strainers on both my boats and have had for decades. Never a failure. Never a leak. Defender or WM will have them.
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Old 29-07-2013, 18:10   #12
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Re: Raw water pump. You can't get there from here

I think brass is a bad idea. There has to be bronze adapters or various ones that can be combined to get what you need. Other wise I would do the plastic type way before brass.

Now I'm only in corrosion control so ...............

PS - there has to be 1"-1/2" brushings available. If not 1"-3/4" brushing to a 3/4" short nipple to a 3/4"-1/2" reducing coupling.

suck it up and go down to West Marine
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Old 29-07-2013, 19:22   #13
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Re: Raw water pump. You can't get there from here

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I think brass is a bad idea. There has to be bronze adapters or various ones that can be combined to get what you need. Other wise I would do the plastic type way before brass.

Now I'm only in corrosion control so ...............

PS - there has to be 1"-1/2" brushings available. If not 1"-3/4" brushing to a 3/4" short nipple to a 3/4"-1/2" reducing coupling.

suck it up and go down to West Marine
The difference between bronze and brass is how much tin or zinc it has in it. More and more bronze now a days is really what was called brass 50 years ago.

Many of the fittings sold at WM are brass, not bronze despite what the signs say. It's getting really hard to find real bronze anymore. Groco has bronze, but I'm betting most the Apollo ball valves sold are what I would call brass. That is more then 7 ish percent zinc.

Almost all bronze has some zinc in it. Its the high zinc content that is really bad. Some valves I've seen from Asia had 25-30 percent zinc and failed after less then a year. This was in landside plumbing /piping, not marine.

Nylon fittings are pretty good, but in my mind, not much better then brass. Pretty weak really. PVC fittings get brittle with age/ heat too.

A agree that brass should not be used for structural fittings, but a single brass bush or two before the hose barb is not that bad. Threaded into a bronze ell its fairly well protected.
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Old 29-07-2013, 19:36   #14
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Re: Raw water pump. You can't get there from here

i'm not joking - bronze casting is dead easy and you can make sure you get the right metal proportions - use a nylon one to make the mould. Might be a bit too lentil and homespun for here, though...
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Old 29-07-2013, 20:14   #15
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Re: Raw water pump. You can't get there from here

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The difference between bronze and brass is how much tin or zinc it has in it. More and more bronze now a days is really what was called brass 50 years ago. I didn't say use fake bronze.


Nylon fittings are pretty good, but in my mind, not much better then brass. Pretty weak really. PVC fittings get brittle with age/ heat too. I would never use PVC, but nylon etc I wouldn't have a problem with.

A agree that brass should not be used for structural fittings, but a single brass bush or two before the hose barb is not that bad. Threaded into a bronze ell its fairly well protected. I disagree that that it is OK to use something that you don't know has failed until it falls apart.
But hey use whatever you want to on your boat. But for me it is not acceptable to make justifications just because it is a little hard to track down the right stuff.

There isn't any reason to try to convince me it OK, saying things are OK instead of correct is a steep slope downward.
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