RV Shower Hot (or cold) water blast

I got the 2017 Thor Chateau 22B Class B out of the hanger and worked on the shower. This is how I fixed the Shower.

It turns out that the hot water was the higher pressure so the blast when opening the dribble valve was scalding hot water.
Therefore the it was too dangerous to use the "turn the shower head towards the wall for a few seconds method.

I have a Oxygenics 26481 Brushed Nickel Body Spa RV Shower Kit installed. Much better the the original equipment piece of ****.
https://www.amazon.com/gp/product/B00AZOWSJM/ref=oh_aui_search_asin_title?ie=UTF8&psc=1

Problem: When turning the dribble valve on after 1 minute, the water was scalding hot for a few seconds until it normalized. Potentially hazardous situation.

First, installed a shut off valve:
https://www.amazon.com/gp/product/B00JQDKTUS/ref=ppx_yo_dt_b_asin_title_o02_s00?ie=UTF8&psc=1
This alone did not fix the problem, but I think it is part of the fix. If allowed to dribble, will fill the hose with the higher pressure water which is HOT.
Next, I installed a Camco 23303 1/2" Back-Flow Preventer
https://www.amazon.com/gp/product/B000EDUTN6/ref=ppx_yo_dt_b_asin_title_o01_s01?ie=UTF8&psc=1
on the cold side behind the control. This is the side with the lower pressure and the hot water would feed back into the cold water line.
That fixed it. The added bonus is that we leave the in the position for the correct shower temp and just use the shut valve.
Installation note: on the Chateau or Four Winds there is a clearance issue when installing the Back-Flow Preventer on the cold water. The hot water had clearance. There are several ways to fix it. I took the easy way out and flipped the faucet over to get the clearance on the cold.

I believe in the KISS system. I just point the shower head at the shower wall for a second.

My shower head has a small drizzle when shut off at head. Solved that problem and boosted pressure. oxygenics head.

My original shower head would shut off completely and cause the hot water blast. I replaced it with a dribble shut off shower head and the problem went away.

AlwaysDreaming wrote:

pauldub wrote:
I bought a check valve to put in the water line but never did install it. I did install a shutoff valve at the shower head and that has totally cured the cold water blast problem. The problem is caused by the water dribbling from the shower head with the built in shutoff that doesn't fully shut off. Just add an inline shut off and all is good and it's easy to do. I bought the KES Shower Head Shut-Off Valve Brass with Metal Handle Polished Chrome K1140B3 from Amazon for about $12.

I have on K1140B3 on order and will try this first, by removing and replacing the dribble valve . If it works, I will return the check valves.
I don't understand why the dribble valve causes the problem, but if replacing it with a shut off works, I don't need to know.
Best Regards, Thanks

I have a shower head with a positive shutoff valve, and it doesn't stop the hot or cold blasts any better than the dribble valves. The blast is caused when the blocked water flow allows either the cold or hot line to back pressure the other line through the open mixer valves due to differences in the pipe runs. That's what causes the momentary blast when you open the shower head valve. Of course if you take too long soaping up, the water in the hose can cool a bit too, but that's usually not enough to be a problem.

pauldub wrote:
I bought a check valve to put in the water line but never did install it. I did install a shutoff valve at the shower head and that has totally cured the cold water blast problem. The problem is caused by the water dribbling from the shower head with the built in shutoff that doesn't fully shut off. Just add an inline shut off and all is good and it's easy to do. I bought the KES Shower Head Shut-Off Valve Brass with Metal Handle Polished Chrome K1140B3 from Amazon for about $12.

I have on K1140B3 on order and will try this first, by removing and replacing the dribble valve . If it works, I will return the check valves.
I don't understand why the dribble valve causes the problem, but if replacing it with a shut off works, I don't need to know.
Best Regards, Thanks

I bought a check valve to put in the water line but never did install it. I did install a shutoff valve at the shower head and that has totally cured the cold water blast problem. The problem is caused by the water dribbling from the shower head with the built in shutoff that doesn't fully shut off. Just add an inline shut off and all is good and it's easy to do. I bought the KES Shower Head Shut-Off Valve Brass with Metal Handle Polished Chrome K1140B3 from Amazon for about $12.

AlwaysDreaming wrote:

Dutch_12078 wrote:
I installed check valves on our shower feed lines to eliminate the backflow issues that cause the hot/cold blast when the shower head shutoff is used.

Thanks. Where did you install check valves? I assume it doesn't matter where you install them?

I installed them as close to the faucet inlets as possible. On my setup, there's only a couple of inches of PEX between the check valves and the faucets. I used SeaTech quick connect valves from Fresh Water Systems, but SharkBite, etc., likely have similar valves.

SeaTech Check Valve - 1/2 CTS

AlwaysDreaming wrote:
Could be interesting for guests. Do I tell them?

Funny story to that... my in-laws were with us. I remembered to warn my father-in-law but somehow forgot to warn my mother-in-law. :B

Maybe consider the ShowerMiser:
https://aquaviewinc.com/rv/

After some more research, this you tube video explains, experiments, and offers a simple cheap fix the best in my opinion.
https://www.youtube.com/watch?time_continue=4&v=BpnNZWdlcfc