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Old 06-02-2018, 06:33 PM   #1
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Dual water source for Tecma flush head

The forward Tecma Head is currently plumbed with raw water flush. Here is a “Y” selector valve for discharge overboard or to the waste tank. This head is always set for discharge overboard, we use the amidships head most of the time, except when traveling. Since I’ve just had to replumb the waste lines due to calcium buildup, I’m thinking about adding a second supply from the freshwater supply, that can be used while at the dock or when there is readily available freshwater. I would have a ball valve shut off on the freshwater supply and also a check valve to prevent accidental seawater ingress should both the raw water and freshwater valves be open simultaneously. Currently there is a seacock shutoff for the raw water supply.

Is this a reasonable approach or a bad idea altogether?
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Old 06-02-2018, 07:16 PM   #2
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Bad idea (though not even close to original). ONLY toilets designed to use onboard fresh water should ever be connected to the fresh water plumbing. Some are designed to use both, but they have totally separate flush water inlet connections. Rerouting a sea water toilet to use fresh water entirely is a no-no that every toilet mfr warns against because bacteria from the bowl can migrate into the fresh water plumbing...alternating between fresh and raw water in a toilet not designed for it not only risks bacteria contamination, it also risks contaminating your potable water supply with sea water.

As for your sea water mineral buildup, there's an easy and inexpensive way to prevent it: Once a week flush a cupful--two at most--of distilled white vinegar all the way through the system. After 45-60 minutes, follow with at least a quart of clean fresh water that you'll add to the bowl.

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Old 06-02-2018, 07:23 PM   #3
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Dual water source for Tecma flush head

Thanks so much for your reply Peggy. I will heed your advice. The amidships head is solely freshwater flush, and I assume is plumbed properly. The forward head is only raw water flush. I should add that the raw water pressure is augmented by a small pump.

I will use the vinegar treatment once per week. Is occasional use of diluted muriatic acid acceptable or is it too strong for this purpose?
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Old 06-02-2018, 09:43 PM   #4
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Weekly doses of distilled white vinegar prevents mineral buildup..muriatic acid is a cure that won't be needed unless prevention is neglected. The problem with "occasional" use of anything is that it doesn't get used until the cure becomes desperately needed.

Distilled white vinegar also has the advantage of being readily available from just about any grocery store, is very inexpensive, can be stored next to food, requires no protective gear to handle it and is environmentally friendly. Muriatic (hydrochloric) acid is none of the above, although it won't harm anything in the system when used occasionally and only as directed.

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Old 06-02-2018, 09:54 PM   #5
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The forward Tecma Head is currently plumbed with raw water flush. Here is a “Y” selector valve for discharge overboard or to the waste tank. This head is always set for discharge overboard, we use the amidships head most of the time, except when traveling. Since I’ve just had to replumb the waste lines due to calcium buildup, I’m thinking about adding a second supply from the freshwater supply, that can be used while at the dock or when there is readily available freshwater. I would have a ball valve shut off on the freshwater supply and also a check valve to prevent accidental seawater ingress should both the raw water and freshwater valves be open simultaneously. Currently there is a seacock shutoff for the raw water supply.

Is this a reasonable approach or a bad idea altogether?
For what it's worth, the Tecma has a double check valve, the flush water enters the bowl well above the water in the bowl and is designed to prevent back flow. Other than owning one, I'm no expert, but I'm not sure how selecting fresh or sea water for the flush water would introduce the possibility of bacterial contamination into the potable water, although the potential for sea water to infiltrate into the potable water might be a reason not to do it, if you forgot to switch to fresh water after using sea water and flush once before turning off the fresh water pump.

I would add that as Peggie noted, cross plumbing sea water lines and fresh water is an invitation for trouble.
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Old 06-03-2018, 04:46 AM   #6
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Assuming the head is capable of correctly using fresh water, which it presumably is since another (identical?) head is already doing so, would you consider a permanent switch to fresh water? That would eliminate any cross contamination risk, keep salt water out of your holding tank, and allow you to ditch the salt water pump and associated lines. The usual concern is fresh water consumption, but you are doing that already using the other head as primary. More heads don't use more water, only more trips to the head.
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Old 06-03-2018, 08:36 AM   #7
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We have been using a salt water/freshwater combo on our Vacuflush for 12 years without a problem. When in port, we use freshwater and switch to saltwater when away. We live on our boat for 4-5 months in the summer and are away from FW sources for about 2/3 of the time. We have a tee plumbed into the Vacuflushwater valve with valves on the inlet sides of the tee. When switching from SW to fresh, I close the SW valve, open the FW and flush fresh water through the system. Other than a set of joker valves and a rebuilding a leaky pump last year-which was older than 12 years-haven't had a problem. Saved a lot of freshwater when we would be out with 6 whale researchers on board for two-three weeks and only 200 gallons of FW.

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Old 06-03-2018, 09:50 AM   #8
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Assuming the head is capable of correctly using fresh water, which it presumably is since another (identical?) head is already doing so, would you consider a permanent switch to fresh water?

Toilets designed to use fresh water are all designed to use pressurized water...they're equipped with vacuum breakers and backflow preventers.. Instead of intake pumps they haves solenoid valves to allow/block the flow the fresh water. So just rerouting the flush water inlet line to a fresh water line won't work without some major modification.

Tator, because your V/F is designed to use pressurized fresh water, your toilet already has the necessary vacuum breaker and water valve installed to protect your potable water supply. However, a tee in the flush water supply line ahead of the toilet's water valve doesn't provide any protection from sea water unless the fresh water pump remains on 24/7/365 to keep the plumbing pressurized. That you've had no contamination--at least none that you're aware of--only proves the truth of "there's a right way, a wrong way and what some guy has gotten away with for years." And there are a lot of guys out there who are that lucky.

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Old 06-03-2018, 10:04 AM   #9
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Assuming the head is capable of correctly using fresh water, which it presumably is since another (identical?) head is already doing so, would you consider a permanent switch to fresh water?

Toilets designed to use fresh water are all designed to use pressurized water...they're equipped with vacuum breakers and backflow preventers.. Instead of intake pumps they haves solenoid valves to allow/block the flow the fresh water. So just rerouting the flush water inlet line to a fresh water line won't work without some major modification.

Tator, because your V/F is designed to use pressurized fresh water, your toilet already has the necessary vacuum breaker and water valve installed to protect your potable water supply. However, a tee in the flush water supply line ahead of the toilet's water valve doesn't provide any protection from sea water unless the fresh water pump remains on 24/7/365 to keep the plumbing pressurized. That you've had no contamination--at least none that you're aware of--only proves the truth of "there's a right way, a wrong way and what some guy has gotten away with for years." And there are a lot of guys out there who are that lucky.

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Tecma provides an option of using raw water (part 38862), which includes a pump. With double check valves and a valve to shut off the raw water a dual supply could be safely plumbed, but why bother. As TT noted, these toilets use very little water when flushing (it's also adjustable), so a fresh water flush will be a lot easier to live with in any case.
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Old 06-03-2018, 10:47 AM   #10
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Dual water source for Tecma flush head

Delfin: I think that is the model of Tecma I have. Ocean Falls and Prince Rupert are the only places in the BC Central/North Coast where we choose to get water. Shearwater’s water is expensive. So we conserve water when we are up there. The forward head is used in remote locations while travelling, or for liquid waste. Otherwise we use the other head that is plumbed to the waste tank.

I think the preventative measure using vinegar is the way to approach this for now. Thanks all!
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