Fresh Water Tank Overflow Mods?

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Fresh Water Tank Overflow Mods?

October 06, 2019, 11:17:01 am

I understand the concern with fresh tank overflow water being dumped down the inside of the wheel well. It's one potential source of water for bulkhead issues that can be avoided by rerouting the drain, as many have done. What I don't understand is how the tank overflow water is a major concern when compared to the road spray that soaks this area every time you drive in the rain. Am I missing something?

Bulkhead issues aren't the only downside to our tank overflow design though. What about the fact that we can only use about 80% of the capacity of our tanks if we plan to actually drive the coach? I typically only fill my tank to about 80% in order to avoid overflowing while traveling. If I fill to 100%, I only have about 80% left when I get where I'm going anyway.

Could a valve in the tank drain line be a potential solution? Why not add a valve to the line, close it after filling to 100%, travel to next destination , open valve? It might require a tank vent to be tee'd into the line somewhere between the valve and the tank for thermal expansion or using water from the tank while traveling, etc. This vent line could be routed out the bulkhead wall and then vertically into the engine compartment high enough to serve it's purpose. Maybe some sort of baffle or restriction at the end of that line to limit the flow and prevent it from becoming a fountain. Or simply route it back down, after an elevated loop, to a safe discharge area.

That seems like a bigger opportunity for extending my boondocking than more hard core solutions like hot water re-circulation or recycling dish water for toilet flushing. Anybody tried anything like this? Any reasons not to? Other solutions to re-claim the full capacity of our tanks while also eliminating this source of bulkhead concern?

Re: Fresh Water Tank Overflow Mods?

Reply #1 – October 06, 2019, 11:23:25 am

Bdale, that overflow line is like the idiot light on a car telling you something is going wrong.
I too as I mentioned before do not fill more than 3/4 but I also use a top fill valve which was added by me (as others have done) to make filling up faster.
I DO NOT walk away while filling, but watch it.
JohnH

Re: Fresh Water Tank Overflow Mods?

Reply #2 – October 06, 2019, 11:27:49 am

I would NOT recommend a valve in the overflow line. Is it not both an overflow line AND the "breather" that allows air in as you empty the tank?

If so, and one forgot to open it when using water, you could implode the tank.

Better solution-- one anyone with a sailboat is familiar with is to route the hose UP to an anti-siphon valve and then down/out clear of the bulkhead.

Re: Fresh Water Tank Overflow Mods?

Reply #3 – October 06, 2019, 11:32:34 am

brett - this is what was installed for me at MOT - fill to top until it runs out of PVC onto ground - drive away. anti siphon valve adds security, but I think overflow would likely stop siphoning on its own in short order as the level drops - we dont "heel" over 30 degrees constant as we run down the road......

Re: Fresh Water Tank Overflow Mods?

Reply #4 – October 06, 2019, 11:39:11 am

Quote from: wolfe10 – October 06, 2019, 11:27:49 am

If so, and one forgot to open it when using water, you could implode the tank.

This was the purpose of the tank vent line that I mentioned. Ok, maybe no valve is needed if the vent line with anti-siphon works. The valve is sort of redundant and unnecessary then.

Re: Fresh Water Tank Overflow Mods?

Reply #5 – October 06, 2019, 11:43:20 am

Regardless, probably not a bad idea to protect end of drain pipe with a bit of insect screen, prevent any upward mobility of the animal kingdom into tank.

Re: Fresh Water Tank Overflow Mods?

Reply #6 – October 06, 2019, 11:45:30 am

Quote from: John Haygarth – October 06, 2019, 11:23:25 am

Bdale, that overflow line is like the idiot light on a car telling you something is going wrong.
I too as I mentioned before do not fill more than 3/4 but I also use a top fill valve which was added by me (as others have done) to make filling up faster.
I DO NOT walk away while filling, but watch it.
JohnH

I also have a direct fill added to my tank. Part of the purpose for adding the valve would be to keep the overflow protection "idiot light" while filling, while allowing the tank to be sealed for traveling. Brett's suggestion of an anti-siphon in the vent line is good. I think keeping the valve would address your concern.

Re: Fresh Water Tank Overflow Mods?

Reply #7 – October 06, 2019, 12:15:43 pm

Bdale,
Not making a recommendation, but here is what I did to address the issue. Probably overthought (like some of my solutions), but it has proven effective. I can fill to max capacity without any overflow coming out. Mind you, I did this when I was reassembling my wet bay and bulkhead project so I had more than the usual access to the areas involved. The usual solutions only seem to address the location of the overflow, which helps protect the bulkhead but does nothing for the sloshing.
Fresh Water Overflow Vent Project
The first picture is from below with the water heater out. You can see the overflow going up through the basement roof and the come back to the original location. The next is the view from inside the closet where you can see the top hat vent and the inside plumbing.
Don

Re: Fresh Water Tank Overflow Mods?

Reply #8 – October 06, 2019, 01:18:16 pm

I installed a gate valve in the overflow which isn't recommended apparently but I got tired of left hand turns costing me water when we are boondocking. I figure it's just like lowering the antenna before traveling. It's just something that you do.
I like the idea of some type venting but haven't seen one that's practical for me.
And besides, I see the need for a 1 1/2" vent when filling but for venting as your using water wouldn't a small 1/4 or 3/8 piece of tubing work ok .. IMHO...

Re: Fresh Water Tank Overflow Mods?

Reply #9 – October 06, 2019, 01:18:42 pm

Bdale, I had mine overflow a few times. I didn't like it. So I did this on my tank to prevent over filling.
Water Fill Valve Auto Shut-off

I have an electric solenoid fill valve so this circuit closes the fill valve when the level reaches the sensor. It could just as easily illuminate a light and sound a buzzer to alert you to stop filling. Adding a 12v solenoid fill valve is a $32 add on.
1/2" NPT Brass Electric Solenoid Valve 12V DC Normally Closed VITON from...

The same sensor can alert you to a low tank level as well. I saw a Prevost that had this 2 sensor level set up. His incoming fill valve was where his fill hose connected and water went directly into the tank. When it was low the fil valve opend and added water to the tank. When it reached the upper sensor the fill valve closed. He used a 120v water pump and tank water all the time.

In our coaches a motorized ball valve at the water supply and the fill valve solenoid can open and close based on water level.

Probably easy enough to get Alex to send you an alert when it is close to full and you can say "Alex, stop filling." The second part is easy.

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Re: Fresh Water Tank Overflow Mods?

Reply #10 – October 06, 2019, 03:02:28 pm

Quote from: Roger & Susan in Home2 – October 06, 2019, 01:18:42 pm

Bdale, I had mine overflow a few times. I didn't like it. So I did this on my tank to prevent over filling.
Water Fill Valve Auto Shut-off

I have an electric solenoid fill valve so this circuit closes the fill valve when the level reaches the sensor. It could just as easily illuminate a light and sound a buzzer to alert you to stop filling. Adding a 12v solenoid fill valve is a $32 add on.
1/2" NPT Brass Electric Solenoid Valve 12V DC Normally Closed VITON from...

The same sensor can alert you to a low tank level as well. I saw a Prevost that had this 2 sensor level set up. His incoming fill valve was where his fill hose connected and water went directly into the tank. When it was low the fil valve opend and added water to the tank. When it reached the upper sensor the fill valve closed. He used a 120v water pump and tank water all the time.

In our coaches a motorized ball valve at the water supply and the fill valve solenoid can open and close based on water level.

Probably easy enough to get Alex to send you an alert when it is close to full and you can say "Alex, stop filling." The second part is easy.

I'm not concerned about over-filling. I can watch the tank level from my wet bay See Level monitor and stop filling easily enough. The goal is to be able to fill 100% without losing 20 gallons of water after filling.

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Re: Fresh Water Tank Overflow Mods?

Reply #11 – October 06, 2019, 03:05:26 pm

Quote from: Bob & Sue – October 06, 2019, 01:18:16 pm

I installed a gate valve in the overflow which isn't recommended apparently but I got tired of left hand turns costing me water when we are boondocking. I figure it's just like lowering the antenna before traveling. It's just something that you do.
I like the idea of some type venting but haven't seen one that's practical for me.
And besides, I see the need for a 1 1/2" vent when filling but for venting as your using water wouldn't a small 1/4 or 3/8 piece of tubing work ok .. IMHO...

What you have done is half of what I have in mind, and you describe the other half pretty much exactly as I see it. Don's solution is probably better but I don't see having that kind of access anytime soon.

Re: Fresh Water Tank Overflow Mods?

Reply #12 – October 07, 2019, 12:03:44 pm

I have been looking at my overflow drain and being I dont want to delve too deep into it I decided to see if I could modify it simply and cheaply. I removed the nipple that is screwed to the rear bulkhead wall on my couch. Yours may be different. I took my big prybar and bent the metal dump louver looking thing out some.
I found a 1/2 PVC nipple that fits inside the original nylon nipple. My plan is to silicone the PVC nipple into the nylon nipple and run a 1/2 PVC pipe down the back bulkhead below the bottom..If I get more motivated I might even build a trap going up into the bathroom closet to keep slosh water loss down. But for now this is my plan. I feel with the 1/2 there will be plenty of venting on the tank so I won't have the thumb over the end of the straw effect. If any of you engineers think otherwise ill step back and punt!

Re: Fresh Water Tank Overflow Mods?

Reply #13 – October 07, 2019, 01:07:56 pm

I guess if you can do it without drilling more holes for mounting the PVC pipe it should work fine. More holes would be more opportunities for road spray to enter the bulkhead. I still don't understand how rain is any less of a problem than the tank overflow but people don't seem to be nearly as concerned about it for some reason.

Re: Fresh Water Tank Overflow Mods?

Reply #14 – October 07, 2019, 01:31:04 pm

Quote from: bdale – October 07, 2019, 01:07:56 pm

I guess if you can do it without drilling more holes for mounting the PVC pipe it should work fine. More holes would be more opportunities for road spray to enter the bulkhead. I still don't understand how rain is any less of a problem than the the tank overflow but people don't seem to be nearly as concerned about it for some reason.

Any water is a concern as far as Im concerned. The water tank overflow dumps straight down the back bulkhead wall directly onto the 1/4 angle iron that the basement floor is rolocked too. There is no sealer between the angle iron and the sheetmetal plate that makes up the rear bulkhead wall.That seam needs to be sealed all across the outside back of that angle iron sheetmetal seam. My coach has flaps on the front side of the tires deflect road spray too some extent. This is just my observation from rebuilding my basement floor.

Re: Fresh Water Tank Overflow Mods?

Reply #15 – October 07, 2019, 01:43:05 pm

Quote from: bdale – October 07, 2019, 01:07:56 pm

I guess if you can do it without drilling more holes for mounting the PVC pipe it should work fine. More holes would be more opportunities for road spray to enter the bulkhead. I still don't understand how rain is any less of a problem than the the tank overflow but people don't seem to be nearly as concerned about it for some reason.

Could it be as easy as a mud flap, Such as some thin conveyor belt material to mitigate spray on the bulkhead surface?

I was thinking about this when I was putting in the Sterling Isolator. Those three batteries get quite the dousing. Was thinking that I could get an old inner tube to fashion a cover secured with the battery lift straps.

Re: Fresh Water Tank Overflow Mods?

Reply #16 – October 07, 2019, 02:11:48 pm

BDale. "guess if you can do it without drilling more holes for mounting the PVC pipe it should work fine. More holes would be more opportunities for road spray to enter the bulkhead. I still don't understand how rain is any less of a problem than the the tank overflow but people don't seem to be nearly as concerned about it for some reason"

I make it a point to not drive in the rain or the dark,, even though I end up doing it occasionally anyway ( thanks DW). Makes me a fair weather traveler ...

There was a comment sometime back from a Foretravel tech that said the roadspray was not the issue. The water intrusion from the inside caused more troubles. Should have screen shot the comment...

Re: Fresh Water Tank Overflow Mods?

Reply #17 – October 07, 2019, 03:22:36 pm

I just rerouted mine through the floor in the water manifold bay about 2" below the floor.

Re: Fresh Water Tank Overflow Mods?

Reply #18 – October 07, 2019, 03:24:37 pm

Quote from: bbeane – October 07, 2019, 03:22:36 pm

I just rerouted mine through the floor in the water manifold bay about 2" below the floor.

That will cure the "watering the rear bulkhead".

If you added an anti-siphon valve (assuming you have an area inside/above where you could mount it, that would add "ain't going to siphon off a full tank when driving". If you do lot of dry camping, this would be worthwhile. If mostly in CG's a waste of time and $$.

Re: Fresh Water Tank Overflow Mods?

Reply #19 – October 07, 2019, 03:45:23 pm

The anti-siphon valves that I am familiar with are typically used in landscaping installations, where a small leak isn't a concern. It's not unusual for them to release a little water occasionally, if not outright leak. Is there another kind of anti-siphon to recommend that doesn't have this issue? Or is this a non-issue due to elevating the valve and it not being required to operate under any sustained pressure, except for maybe the occasional accidental overfill?

Re: Fresh Water Tank Overflow Mods?

Reply #20 – October 07, 2019, 03:48:32 pm

All our sail boats have no leak anti-siphon valves. Particularly important for engine heat exchanger raw water outlet, as when sailing on a heel it is often below waterline.

Were it not for the anti-siphon valve it would back salt water into the engine exhaust elbow and hence into the engine!

Re: Fresh Water Tank Overflow Mods?

Reply #21 – October 07, 2019, 04:40:57 pm

This is how we re-routed our overflow. Link: Another slow water leak
Includes a few pics.

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