# Fill black water tank through-hull?
**URL:** https://nonsuch.discourse.group/t/fill-black-water-tank-through-hull/10249
**Category:** General
**Created:** [March 2, 2026, 1:23am UTC](https://nonsuch.discourse.group/t/fill-black-water-tank-through-hull/10249 "2026-03-02T01:23:24Z")
**Posts on this page:** 8
**Page:** 1
### Author:  [@NS30Loon](https://nonsuch.discourse.group/u/NS30Loon)
#### Post date: [March 2, 2026, 1:23am UTC](https://nonsuch.discourse.group/t/fill-black-water-tank-through-hull/10249/1 "2026-03-02T01:23:24Z")
Greetings and ahoy! We replaced our black water system with a composting head last season. I capped the intake through-hull valve on the inside. Should we remove the through-hull valve and fiberglass the hole while LOON is out of the water? Maybe re-plumb as a salt water foot pump to the galley sink? Thank you!
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### Author:  [@NS233\_Bob\_Neches](https://nonsuch.discourse.group/u/NS233_Bob_Neches)
#### Post date: [March 2, 2026, 1:29am UTC](https://nonsuch.discourse.group/t/fill-black-water-tank-through-hull/10249/2 "2026-03-02T01:29:42Z")
IMHO, it depends on how much you care about performance (minor impact), risk of plug failure (manageable), and effect on resale value (if you plan to sell, some buyers may not like composting toilets and appreciate that you’ve left it easy to revert).
My $0.015 cents.
– Bob
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### Author:  [@RonB](https://nonsuch.discourse.group/u/RonB)
#### Post date: [March 2, 2026, 3:40am UTC](https://nonsuch.discourse.group/t/fill-black-water-tank-through-hull/10249/3 "2026-03-02T03:40:21Z")
Totally agree with what Bob said.
RonB.
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### Author:  [@NS233\_Bob\_Neches](https://nonsuch.discourse.group/u/NS233_Bob_Neches)
#### Post date: [March 2, 2026, 3:49am UTC](https://nonsuch.discourse.group/t/fill-black-water-tank-through-hull/10249/4 "2026-03-02T03:49:42Z")
FWIW, here’s a picture of how I plugged the raw water intake that was rendered unnecessary by conversion to electric.
I’m comfortable with the safety of leaving it that way. Others mileage may vary.
 – Bob
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### Author:  [@Rendezvous](https://nonsuch.discourse.group/u/Rendezvous)
#### Post date: [March 2, 2026, 7:44pm UTC](https://nonsuch.discourse.group/t/fill-black-water-tank-through-hull/10249/5 "2026-03-02T19:44:31Z")
When we went composting, we capped the intake and I believe plugged the holding discharge. There were no hoses and no clamps (and Bob - isn’t your hose a below waterline hose needing to be double clamped?). A few years back, we stripped the bottom paint off and while we were at it, had them glass over the two openings, as well as the one for the original depth sounder - we now use a tri-ducer instead of separate depth and speed transducers. I feel more comfortable having glassed them over. Makes the cabinet under the sink a bit more useful.
What I did not do when I painted the deck was glass over the holding tank pump-out. Not sure why I didn’t think of that at the time. A leak there will probably not sink the boat.
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### Author:  [@PaulM](https://nonsuch.discourse.group/u/PaulM)
#### Post date: [March 2, 2026, 9:52pm UTC](https://nonsuch.discourse.group/t/fill-black-water-tank-through-hull/10249/6 "2026-03-02T21:52:48Z")
I repurposed mine for a wash down pump on the foredeck.
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### Author:  [@Aloki329](https://nonsuch.discourse.group/u/Aloki329)
#### Post date: [March 3, 2026, 12:41am UTC](https://nonsuch.discourse.group/t/fill-black-water-tank-through-hull/10249/7 "2026-03-03T00:41:09Z")
My personal opinion -
- If you want to keep the seacock there , remove the pipe to hose coupling and put in a marlon plug.
- If you don’t want/ need to keep the seacock , remove same and put a Marlon cap.
- Best , Gary
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### Author:  [@RonB](https://nonsuch.discourse.group/u/RonB)
#### Post date: [March 3, 2026, 1:43am UTC](https://nonsuch.discourse.group/t/fill-black-water-tank-through-hull/10249/8 "2026-03-03T01:43:46Z")
When I put the composter on my Ericson (still for sale) I removed the valve and just capped the through hull. I figured there were fewer parts to fail that way.
I’ll do the same on the 26 as the composter is far better than any holding tank set up.
RonB.