Pressure Regulator for Black Tank Flush??

[Randel J]

I know this is a non-issue, but I am curious. Why isn't a pressure regulator recommended for the black tank flush? If it is a straight line from the inlet to the black tank, then no problem. But many trailer models will have at least one 90-degree turn in the line, so could high water pressure cause a problem?

Just curious.

[ARoamer]

I'd think it's that the flush line is always open, it can't build up too much pressure unless the supply pressure is extremely high. I don't believe elbows would slow flow enough to contribute to excessive pressure either.

[RedHorse1]

I’d also expect the flush has a smaller orafice so it will “spray”. That’d be the flow limiting point and would keep the water pressure up in the rest of the fresh plumbing. I’ve never had water pressure complaints while flushing the black tank.

[SloPoke]

Originally Posted by Randel J

I know this is a non-issue, but I am curious. Why isn't a pressure regulator recommended for the black tank flush? If it is a straight line from the inlet to the black tank, then no problem. But many trailer models will have at least one 90-degree turn in the line, so could high water pressure cause a problem?

Just curious.

You are NOT confused, not at all... YES, a pressure regulator is a good idea. We were in a RV Park in Iowa and hooked up the Black Flush fitting to a second spigot at the park and bypassed our usual setup where we use pressure regulated water to flush our black tank.

The outcome was a blown check-valve in the black tank flush line that is installed by Jayco under the bathroom sink. It was a mistake we will never make again as the entire undersink was sprayed with high pressure water from the black flush line that split the plastic check valve. The only fortunate thing in this learning experience was that it was easy to hear the check-valve explode and the water running - and I shut it off in seconds. We mopped up the wet-mess and dried out the bathroom sink cabinet right away before we had any serious damage.

[LuckyDuck]

We, too, use a pressure regulator on the black tank flush hose. It’s just an inexpensive fixed-flow one that stays with the hose, but provides a bit of insurance. We use an adjustable regulator for the city-connect feed.

[ARoamer]

Originally Posted by SloPoke

You are NOT confused, not at all... YES, a pressure regulator is a good idea. We were in a RV Park in Iowa and hooked up the Black Flush fitting to a second spigot at the park and bypassed our usual setup where we use pressure regulated water to flush our black tank.

The outcome was a blown check-valve in the black tank flush line that is installed by Jayco under the bathroom sink. It was a mistake we will never make again as the entire undersink was sprayed with high pressure water from the black flush line that split the plastic check valve. The only fortunate thing in this learning experience was that it was easy to hear the check-valve explode and the water running - and I shut it off in seconds. We mopped up the wet-mess and dried out the bathroom sink cabinet right away before we had any serious damage.

What do you think was the cause, high water supply pressure, a low quality check valve, possible freeze damage?? Not sure what Jayco uses, this one (made in the USA) is rated for 125PSI-

[Bill Johnson]

I bet it was a bad check valve, look next time at the pressure gauge when someone is using water in the camper and the pressure drops with any water running

[Happy wife / happy life]

I had never thought about to much water pressure at the black water hose. I think I’ll follow “ LuckyDuck’s” suggestion and install an inexpensive in line regulator to my black water flush hose.

[Jay2504]

On my unit, a 2020 24RBS, that valve was in the outside kitchen compartment. It got replaced with a elbow before it was ever used. I had one go bad in the previous camper. If “bad” water can climb up 5 feet and turn a 90 degree corner, then get past the check valve at the hose connection, then I deserve to die. Lol

[TWP723]

A black tank flush is straight to the tank and is a open system with maybe a sprinkler at the end. My Montana does have a check valve inline. Therefore, no pressure to build up. In my opinion, the more pressure the better.

[Docsouce]

I have a 2020 26XD. I Followed the black water flush plumbing and as far as I could and it seems like an isolated system. I didn't find a check valve. It has its own water feed and it's not hooked to the water control center. To flush I use a separate hose with a Camco pressure regulator on it. It probably doesn't need the regulator but I just don't want to take the chance of blowing the line at one of these campgrounds that had 110 psi water pressure.
Also as someone mentioned here in a previous post, when winterizing I pump antifreeze through the flush line with a hand pump until I hear the antifreeze entering the tank. I'm sure I could blow it out with air but this is the method I prefer.

[SloPoke]

Originally Posted by ARoamer

What do you think was the cause, high water supply pressure, a low quality check valve, possible freeze damage?? Not sure what Jayco uses, this one (made in the USA) is rated for 125PSI-

I remember that the water pressure at this park was really high, the check valve was the original installed in the Seneca and it never was exposed to freezing as we were travelling across the country for about 6 months. I can only estimate that it was due to pressure, that's why I have made sure to use pressure regulated water supply ever since - and no issues afterwards.

[Bill Johnson]

Originally Posted by Docsouce

I have a 2020 26XD. I Followed the black water flush plumbing and as far as I could and it seems like an isolated system. I didn't find a check valve. It has its own water feed and it's not hooked to the water control center. To flush I use a separate hose with a Camco pressure regulator on it. It probably doesn't need the regulator but I just don't want to take the chance of blowing the line at one of these campgrounds that had 110 psi water pressure.
Also as someone mentioned here in a previous post, when winterizing I pump antifreeze through the flush line with a hand pump until I hear the antifreeze entering the tank. I'm sure I could blow it out with air but this is the method I prefer.

I have a bore scope and 20 feet of cable and it goes directly to the black tank, I don't understand why it wood be connected to anything else. My San-T-Flush connector is mounted to a metal plate behind the plate is a hose connection for like under the sink for a faucet. The factory connected a 6 foot faucet supply hose to a PEX connector 16 inches away, (I replaced the hose with a short one that just fit) the Pex goes across my compartment turns and goes all the way across the motorhome and goes directly into the end of the black tank. It never goes into the RV there is no reason for it to go inside

[SloPoke]

Originally Posted by Bill Johnson

I have a bore scope and 20 feet of cable and it goes directly to the black tank, I don't understand why it wood be connected to anything else. My San-T-Flush connector is mounted to a metal plate behind the plate is a hose connection for like under the sink for a faucet. The factory connected a 6 foot faucet supply hose to a PEX connector 16 inches away, (I replaced the hose with a short one that just fit) the Pex goes across my compartment turns and goes all the way across the motorhome and goes directly into the end of the black tank. It never goes into the RV there is no reason for it to go inside

The Seneca design is published in the attached document

[Randel J]

Wow, this conversation has been very enlightening! I'm now going to buy a cheap pressure regulator for my black tank flush hose

[Bill Johnson]

This is mine

[SloPoke]

Originally Posted by Randel J

Wow, this conversation has been very enlightening! I'm now going to buy a cheap pressure regulator for my black tank flush hose

While you will find a lot of differing opinions on the forum, you will also find that many of those different opinions are based on different manufacturers, makes and models of RV's, and the owners experiences with using them. Many RV makes and models use the same supply of parts, and some don't, and now it appears that some don't even put all of the safety / backflow devices that others might use into their products. Take it all with a view of what you intend to do, with your own personal intentions of how you plan to travel.

We have been stuck a few times when stuff breaks, and having to chase down parts/repairs while hundreds/thousands of miles away from home, and other times we can just say "well, the black tank flush will be broken for a while until I can get this fixed" and we keep on our travel plan. ...

Ultimately, our goal is to explore-travel-wander with as few mishaps/leaks/breaks as possible. Sometimes those breaks/mishaps are preventable with a protection device like a pressure regulator or(Electrical EMS, Surge protector, water filter... etc) to keep you from having that happen (or happen again)... The most important thing... get out and go... not all things that break for us, will break for you... have fun trying!

[David_ski]

My black tank flush does not go straight to the black tank. It first goes up the wall with the hot and cold shower PEX and then back down to the black tank. I presume there is a check valve at the turnaround point.

[DonLegg]

I use a wye connector with shutoffs connected to my pressure reducer at the spigot so both fresh and black tank hoses are pressure restricted. If there are twin spigots I connect the black tank hose to a separate spigot after concluding that the water pressure is not excesive. The RV's black tank hose connection has a back flow preventer. I have a pressure gauge I can use too if I have any doubts about the water pressure. Note: I have eliminated the anti-siphon valve in the black tank line under the bath sink as it was staring to leak and I read that even new ones can leak.

[Poppyof5]

Originally Posted by LuckyDuck

We, too, use a pressure regulator on the black tank flush hose. It’s just an inexpensive fixed-flow one that stays with the hose, but provides a bit of insurance. We use an adjustable regulator for the city-connect feed.

Just courtesy, I always open the black tank before turning the flush water on. Wouldn’t that take care of to much pressure when flushing? Adding a regulator is an easy fix but still wondering.