Old holding tank; Galley seawater from head thru-hull

[idearat]

First, thanks to Peggie for your excellent advice! I bought your book and have scoured this site, and it's proving invaluable now that I'm redoing my old boat's head plumbing.

Now I have a couple of questions.

1) Holding tank: as far as I know the tank in the boat is original (1975), and was plumbed originally as a holding tank. Not sure it was ever used that way, but I hope not: at some point it was replumbed for fresh water. 2 inspection ports were cut in the top (~10"x6", with screw-out 4" access ports), a mushroom added in the bottom.

I'm trying to decide whether to reuse the tank, which seems solid and well-built, but will need some holes filled (there's a plastics shop in town that does it) and new fittings added (esp. bigger vents!). Is there anything I might be overlooking that would make that a bad idea? I'm assuming Poly tanks don't simply 'wear out'.

2) There's a seawater foot pump in the galley, which we use for bulk cleaning... e.g. soaking pots before washing. It's currently plumbed to a T in the head inlet, right by the through-hull. I know you caution strongly against connecting any manual head inlet to the boat's potable water; would you have the same concerns here?

(Short of a new through-hull, my only other option is a T in the engine intake, and I have concerns about that... which I'll address in the appropriate forum if it comes to that.)

Thanks... Perry.

 

[Peggie Hall HeadMistress]

If tank walls are thick enough you can convert it to waste holding...

Walls need to be about 3/8" or very close to that thickness to support the weight of the contents. If it's been used to hold water and hasn't bulged, it's thick enough. You shouldn't need a plastics shop to seal existing fittings if they're threaded...all you need is a threaded plug wrapped in plenty of Teflon tape. Not that hard to install new fittings yourself either. I would invest in new o-rings for the inspection ports.

I have no idea what you mean by "a mushroom" in the bottom of the tank.

Using the same thru-hull for both toilet flush water and water--even sea water-going into your galley sink isn't as bad a connecting the toilet to a supply of water stored onboard, but I'm not crazy about the idea. And I definitely would NOT use the engine intake...that's just asking for trouble! But you may have an option you haven't considered: tee the head intake line into the head sink drain line, freeing up the head intake thru-hull for exclusive use by your galley foot pump. That would also provide a means of flushing all the sea water out of the head and head plumbing with fresh water.

 

[idearat]

Hi Peggie.

I haven't been able to measure the tank wall yet, but as you say it's been holding water with no bulges, so I assume it's okay.

None of the fittings are threaded. The head inlet and outet are black plastic pipe, welded in near the tank top (the outlet has a draw-pipe), with only about 1" of straight pipe sticking out... I'm hoping it's normal black plumbing pipe I can glue fittings to. There's a third one that's badly plugged that I want removed and patched (or I guess I could glue a plug on).

By 'mushroom' I meant a small plastic through-hull: they just drilled a hole in the bottom and installed a through-hull with the nut and hose barb on the outside. I need to remove that and (because it's in the bottom) make darn sure the hole's properly blocked... hence the plastics shop. Or is there another way to reliably fill a hole like that?

I also need the old welded-on 1/4" vent hose barbs removed and filled; I'll install two new 3/4" vents (through-hull mushroom thingies) myself. And yes, definitely new o-rings for the inspection plates.

Re the water supply, I like your option, except I'm removing the head sink (a leaky fold-out thing) in favour of the 3-step walk to the galley sink. I'm also going to re-purpose the head sink drain through-hull for the galley sink, which is currently plumbed into a cockpit drain, which strikes me as a very bad idea! I could perhaps tee the head inlet into the GALLEY sink drain... hmm... need to think about that. Could be the best long-term solution (once I get around to re-jigging the nightmarish cockpit drains).

Thanks for the suggestions!

Perry.

 

[Peggie Hall HeadMistress]

Aha! Mushroom thru-hull..

That's what's included in the "fittings relocation kits" and actually work pretty well. Till I discovered the Uniseal (take a look at it here UNISEAL scroll through ALL the pages), that was what I recommended, however with rubber gaskets under the flange on the outside of the tank an the nut on the inside.

A few more observations:

You've convinced me that you DO need a plastics fabricator after all...hopefully one with a spin welder.

Go with a 1" vent...Depending upon it's length and routing, you may be able to go with just one. Two doesn't always help if they're too long, have too many bends the thruhulls are in the wrong place. We can talk about that if you want to.

And finally, I'm not really thrilled with teeing the head intake into the galley sink drain, but I like it a lot better than using the same thru-hull to supply the water for the sink and the toilet.

Send me an email if you'd like some one-on-one help spec'ing out the fittings.

and if you have the clearance above the tank (you need at least 5") put ALL your tank fittings on the top of the tank with a pickup tube inside the tank on the discharge.

 

[alexco38]

T off from the head flush inlet seacock

Peggy,

I have read you book cover to cover and also frequent observer to this forum.

You stated not really thrilled with teeing the head intake into the galley sink drain, but like it a lot better than using the same thru-hull to supply the water for the sink and the toilet.

I don't have the option to T off from the galley sink.

I like to put a bronze one-way valve for the head intake hose and T off from the same seacock a raw water hose for a hand pump for the galley sink.

The bronze one-way value is commercial grade and very robust. The hand pump at the galley sink only use to draw raw water for pre-washing dishes. I'll rince them with tank water after.

Do you see down side to this plan. You opinion is highly valuable.

 

[Peggie Hall HeadMistress]

If your galley sink can drain...

You DO have the option of teeing the head intake into that drain line.

Or, if you have a sink in the head, the head sink drain line would be the best choice. The galley sink should only be used if it's the only sink.

You quoted me as saying "...not really thrilled with teeing the head intake into the galley sink drain, but like it a lot better than using the same thru-hull to supply the water for the sink and the toilet"...which is exactly what you want to do, and what you just quoted me as saying I don't like.

I'm not really thrilled with the idea of ANY common plumbing for the toilet and galley...bacteria can migrate and just rinsing with fresh water won't kill 'em. But connecting the toilet intake to a drain line is safer than using the same line to to supply water to the sink and toilet 'cuz at least the sink drain only carries water that's already been used.

 

[alexco38]

Sink Drain

Yes I can move the head intake to a T off the sink drain in the head. Then I can use the existing seacock to run a long hose to the Raw water hand pump in the galley.

I agree with you. It is much safer.

Thank you for the rapid response and insight.

 

[Peggie Hall HeadMistress]

There you go! That'll work.

Fwiw, several boat builders use the same thru-hull/seacock for both the head sink drain and the head intake because it eliminates a hole in the boat and saves 'em the cost of the thru-hull seacock.