US1 Fountain

iTrader: (1)

Is this a no no?

Thru hull for an A/C unit. Prefer the looks of the S/S thru hull over the bronze one, but will be attaching a bronze valve directly to it. Not sure about this dissimilar metals and the corrosion issues.
Fresh water use only.

Also, how do they attach a shut off valve that has NPT threads, while the thur hulls have NPS threads, plenty of sealer? I know they will screw on to eacch other, but just not the idea setup.

Thanks

f311fr1

The bronze is a less noble material and will fail before the SS. Just buy a SS ball valve at a large wholesale plumbing supply house. NPT has a taper and NPS has a taper but also seals with a ball or globe shape in a socket. It should seal with some locktite pipe sealant for SS. Make sure it is for SS.

US1 Fountain

iTrader: (1)

NPT=National Pipe Taper thread
NPS=National Pipe Straight thread. Ex: Straight threads for bulk head thru type of use with nuts on both sides.
As I have always understood it to be.

Thanks for the other info. I may just go bronze on the thru hull since that appears to be the norm, plus it won't be seen anyways.

rdoactive

I dont know enough about dissimilar metals and corrosion, so I just never mix them.
As for the threading, there are shutoff valves made specifically for that threading and application. They usually have a flat flange to butt against the inside of the hull. I've only found these at marine suppliers.
Never do underwater fitting half a$$ed.
Gary

Crazyhorse

Make sure the through-hull fitting is wired to the rest of the bonding system in the boat. If there isn't a green wire fastened to the fitting you'll want to run one to the nearest metal fitting/ fixture that does have one, such as an engine block, water heater, sea strainer.

US1 Fountain

iTrader: (1)

The bonding was the next question. I thought that it would need it. The strainer will more than likely be a Groco plastic one, or their bronze one. Depends if it is installed in the cabin hidden or in sight in the bilge.

Wonder why the thru hulls needed to be bonded, but I have never heard of the drain plugs being bonded.

Crazyhorse

Yup, the drain plug fitting is, or should be if it's not already, tied in with the bonding system. Anything metallic, fuel fills, through-hull fittings, drives, trim tabs/K-planes, water heater, engines, sea strainers, raw water shutoff valves, swim platform, should be tied in.

MOP

As long as the two are in good contact with each other and protected together by bonding or their own Zinc bronze and stainless are very happy together. There are millions of boats/yachts with stainless shafts, bronze props and struts, they are routinely protected by just one shaft zinc and last for many years doing so.