Water Tank Access

Apr 11, 2018
71
Hunter 340 Dowry Creek, NC
Morning, all. Sequoyah is a '99 H340. The potable water tank is beneath the V berth. Access to the top of it can be had through two hatches, but they offer none to the tank's stern side. There is no way I see to do it through the sole, which is solid glass beneath a thin layer of teak & holly ply, or the cabinetry. It may be possible by unscrewing and lifting up the Melamine-surfaced plywood that forms the platform on which the V cushions go, but I've yet to try it.

What I'd like to do is replace the old polybutylene piping in the plumbing system with PEX, requiring access to the drain fitting on that tank. I assume (only, not having got to it) that's located at the stern side bottom. Has anyone had occasion to find out? How did you get to that spot? What is the fitting you found there: 1/2", threaded, barbed?
 
Nov 6, 2006
9,884
Hunter 34 Mandeville Louisiana
Just a note.. The polybutylene got its bad reputation from being laid in the attics of houses where it saw a lot of high temperature and radiant heat as well. In locations that are relatively cool, the stuff is fine and lasts a while.. The original system in my '85 model boat is fine.. we have some summer heat, but the lines being in the bilge mostly do not see enough temperature to fail them.. they will break if water is allowed to freeze inside, but again the temperature in the bilge is moderated by seawater (or bayou water in my case) temperature. Being a "cheap ash" engineer, I am not a fan of fixing things that aren't broken.
Of course, your boat, your choice..
 
Apr 11, 2018
71
Hunter 340 Dowry Creek, NC
Just a note..
It's an overkill project here. I'm replacing the water heater because the old Seaward was leaky. Got an Isotemp at a good price and decided while I was into the plumbing I'd also replace the noisy, low-flow pump, which wanted a new strainer mated to it, and naturally new water lines surrounding those devices. That's not far from half the whole blamed system, so ...

I'm going with PEX and push-on fittings to make it easier to work on the system in the future, and since I was doing all that it occurred to me that replacing the two or three feet of line between a cutoff valve and the water tank would just get that much more of it done and presumably behind me for years more. I hadn't anticipated the problem of access to the tank fitting, but, you know, it's a boat. The only thing you can count on is running into things you don't count on.

Later today I'm going to run a borescope down through the near hatch in the v berth to get a look at the location and nature of the tank's outlet. After that I'll better know how to proceed.

Thanks for the knowledgeable comment about the reliability of polybutylene in benign conditions, by the way. If it's too difficult to get that segment of line replaced I'll just leave it alone until it gives trouble. After all, how much harm could it do? The tank holds only 75 gallons. Even were it full, and the line to burst, the bilge pump could handle it.
 
Last edited:
May 13, 2013
16
Hunter 336 Windsor
It's an overkill project here. I'm replacing the water heater because the old Seaward was leaky. Got an Isotemp at a good price and decided while I was into the plumbing I'd also replace the noisy, low-flow pump, which wanted a new strainer mated to it, and naturally new water lines surrounding those devices. That's not far from half the whole blamed system, so ...

I'm going with PEX and push-on fittings to make it easier to work on the system in the future, and since I was doing all that it occurred to me that replacing the two or three feet of line between a cutoff valve and the water tank would just get that much more of it done and presumably behind me for years more. I hadn't anticipated the problem of access to the tank fitting, but, you know, it's a boat. The only thing you can count on is running into things you don't count on.

Later today I'm going to run a borescope down through the near hatch in the v berth to get a look at the location and nature of the tank's outlet. After that I'll better know how to proceed.

Thanks for the knowledgeable comment about the reliability of polybutylene in benign conditions, by the way. If it's too difficult to get that segment of line replaced I'll just leave it alone until it gives trouble. After all, how much harm could it do? The tank holds only 75 gallons. Even were it full, and the line to burst, the bilge pump could handle it.

i'm doing this project now..
I have to agree with you!! if it aint broke...
I will be running pex after the water pump to a three way pex, to a pex shut off valve to the hot water intake via a pex to npt female, and not touching the pb outflow from the hot water tank.
from the other side of the tee i'll run pex to a male npt and tie into the pb again..
this'll work right?
then for winterization i just turn the valve off to bypass the tank..
cheers