Tape or sealant for vented loop?

[PeterK]

Literally had a shitty day yesterday. A vented loop failled on the discharge side of one of my heads. All cleaned up but one of the worst events I've experienced aboard... Amazing how far this could splatter...

Sam's had the loops I need (white plastic) and I'll hopefully get them today (God bless Steve- he always has time for my issues and resolves them immediatley!). My question is best practice to seal/lubricate the plastic to galvinized (the elbows). PTEF tape or sealant? Is sealant, any brands recommended? I will be taking the preventative course and changing all the loops... Once crapped on, twice shy...

 

[KPTIM]

When making up a metal to plastic tapered pipe joint you should strongly consider using a pipe sealant design for plastic / non-metalic pipe thread joints. Loctite makes a product for this "MR 5438", there are others but make sure they fit the application.

Teflon tape and pipe dopes are designed for metal on metal joints NOT plastic to plastic or plastic to metal joints. These products make the joints more slippery during assembly inviting the tendency to over tighten the joint. More important is that these products add solid materials/fillers to the joint that are difficult to displace while tightening the joint. This can cause extreme pressures on the tapered plastic fitting and cause them to crack.

You also need to make sure that the sealing product selected does not contain oils or solvents that will damage or weaken the plastic fitting.

Tim

 

[bobk]

You want to be sure the plastic part is NOT an acetal like Celcon or Delrin. Contact with a zinc-containing metal can lead to corrosion of the acetal under some circumstances. This was a problem in the early days of 'PB plumbing'.

Bobk

 

[PeterK]

When making up a metal to plastic tapered pipe joint you should strongly consider using a pipe sealant design for plastic / non-metalic pipe thread joints. Loctite makes a product for this "MR 5438", there are others but make sure they fit the application.

Teflon tape and pipe dopes are designed for metal on metal joints NOT plastic to plastic or plastic to metal joints. These products make the joints more slippery during assembly inviting the tendency to over tighten the joint. More important is that these products add solid materials/fillers to the joint that are difficult to displace while tightening the joint. This can cause extreme pressures on the tapered plastic fitting and cause them to crack.

You also need to make sure that the sealing product selected does not contain oils or solvents that will damage or weaken the plastic fitting.

Tim

Thanks Tim. Exactly what I needed to know!

You want to be sure the plastic part is NOT an acetal like Celcon or Delrin. Contact with a zinc-containing metal can lead to corrosion of the acetal under some circumstances. This was a problem in the early days of 'PB plumbing'.

Bobk

Bob, exact duplicate of the OEM. Not sure what type of plastic it is but Hatteras used it before.

BTW Thought I'd update on how I cleaned up. Flushed with a lots of fresh water- excess ran back to a bilge in my ER. Wet vacuumed affected area and bilge ( dumped in a land based toilet). I did not want to use any chlorine as there is electrical in the space affected so sprayed first with straight white vinegar followed up with Hydrogen peroxide. The odor was actually gone after the straight water rinse, but wanted to make sure I disinfected everything.

 

[bobk]

Hmm... you had a plastic part fail. Was the failure near the galvanized pipe? And, I'd bet the galvanized pipe was not OEM.

Bobk

 

[Fair Well]

I had the same thing happen about two years ago. I decided to build my own and vent them into the engine room vent box. At least that way if the valve fails it well poop out side Can't seem to rotate the pic but you get the idea.

 

[PeterK]

Figured out how to post a pic. Had to turn off "enhanced attachment uploading" in the general settings!

Here is a pic of the loops. I am replaced all of the white nylon valves (1 fails- the others can't be far behind...)

 

[PeterK]

BobK you were correct, not glavanized but bronze. New bulkhead clamps, hose clamps, Rectorseal T-2 on all four valve. Had to pull a cabinet behind the bowl, climb in a small opening and sit in the Glendening tub but got them done.

Tested them and now know the hoses are going to have to be done as well. The hose on the discharge side of one of the heads lurches against the clamps when flushed... Not looking forward to the next round of boat yoga for that one but it will beat the hell out of another shit storm...