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Tinman97423 · 06-12-2016, 09:57 AM

Cold water blast in shower..
The blast of cold water has to be stopped at the shower cold/hot valve. I am not talking about the on/off valve at shower head. Think about this! When you close the valve at the shower head the cold water has more pressure behind it that the hot water coming from the heater. That means cold water will push the hot water back into the tubing until both hot and cold pressure equalize. There is about 6 feet of tubing from the shower valve to the heater where the cold water might push back the hot only in the tubing. It might push back about 1 to 1 ½ feet. There is a check valve on the hot water side of the heater (to keep anti freeze out of the heater). YOU NEED A CHECK VALVE AS CLOSE TO THE SHOWER VALVE AS POSSIBLE ON THE HOT WATER SIDE.
I have read about this once in Trailer Life and Motor Home magazines that verified my thinking about the cold blast.
My 2016 Cougar 303SLR has a hot water line coming from the heater up to the shower and is around 6 to 7 feet long. Before starting don’t forget to DRAIN the hot water side by opening a hot water valve at the bathroom sink or shower and then the drain valve under the trailer. I removed the shower valve VERY CAREFULLY using a plastic putty knife to remove the silicone around the valve housing. AGAIN be very careful when doing this because of NO backing for the four screws that hold the valve to just 1/16 inch of fiberglass backing. You should be able to remove the hot water connection with your fingers. Do not pull it out at this time. In the compartment below remove side panels and look to the upper left of the water heater near the force air heater and you will see the Hot (red) and Cold (blue) lines coming from the shower. Follow them towards the heater and where you have room to cut the Hot side (red) leaving at least 10 inch of tubing on both ends if cutting near an existing fitting. Back in the shower pull the hot line up about a foot (DO NOT PULL IT SO FAR THAT YOU PULL THE OTHER END INTO THE WALL. YOU MIGHT NOT GET IT BACK THROUGH)
Cut the line about 6 inch from the connector and at this point install the CHECK VALVE. Push the line back into the wall and connect it back to the shower valve. Now go back down and reconnect the hot supply using a coupler. I did not need to cut out the amount from the added fittings because there was plenty of room for the extra length of the fittings.
I now have about a 1 second spot of cold before the preset temp comes back. WHAT A DIFFERENCE…..

I found all of the fittings I needed at zoro.com that claims to have more than 300,000 fittings. Everything cost about $15 including shipping.

The coupler, ½” CTS, PEX, White Product Number G4389287 Stock #16T737 PE10420.
Along with the coupler be sure to get the Coupler ½” inserts Product Number G4388255 Stock # 16T768 (Two each).

Check Valve, Polysulfone, ½ inch Product Number G2781064
Stock # 1DAT2 (No inserts needed with check valve)
PLEASE CALL THEM TO CHECK THE NUMBERS
These fittings are for PEX tubing.
PLEASE check these numbers before ordering just incase I have made a typing mistake.
This should work on any RV if you can locate the shower water lines going into the heater and there is room to cut/add coupling.

06-12-2016, 09:57 AM	#19
Tinman97423 Junior Member Join Date: Oct 2015 Location: Coos County Posts: 28	Shower cold water blast Cold water blast in shower.. The blast of cold water has to be stopped at the shower cold/hot valve. I am not talking about the on/off valve at shower head. Think about this! When you close the valve at the shower head the cold water has more pressure behind it that the hot water coming from the heater. That means cold water will push the hot water back into the tubing until both hot and cold pressure equalize. There is about 6 feet of tubing from the shower valve to the heater where the cold water might push back the hot only in the tubing. It might push back about 1 to 1 ½ feet. There is a check valve on the hot water side of the heater (to keep anti freeze out of the heater). YOU NEED A CHECK VALVE AS CLOSE TO THE SHOWER VALVE AS POSSIBLE ON THE HOT WATER SIDE. I have read about this once in Trailer Life and Motor Home magazines that verified my thinking about the cold blast. My 2016 Cougar 303SLR has a hot water line coming from the heater up to the shower and is around 6 to 7 feet long. Before starting don’t forget to DRAIN the hot water side by opening a hot water valve at the bathroom sink or shower and then the drain valve under the trailer. I removed the shower valve VERY CAREFULLY using a plastic putty knife to remove the silicone around the valve housing. AGAIN be very careful when doing this because of NO backing for the four screws that hold the valve to just 1/16 inch of fiberglass backing. You should be able to remove the hot water connection with your fingers. Do not pull it out at this time. In the compartment below remove side panels and look to the upper left of the water heater near the force air heater and you will see the Hot (red) and Cold (blue) lines coming from the shower. Follow them towards the heater and where you have room to cut the Hot side (red) leaving at least 10 inch of tubing on both ends if cutting near an existing fitting. Back in the shower pull the hot line up about a foot (DO NOT PULL IT SO FAR THAT YOU PULL THE OTHER END INTO THE WALL. YOU MIGHT NOT GET IT BACK THROUGH) Cut the line about 6 inch from the connector and at this point install the CHECK VALVE. Push the line back into the wall and connect it back to the shower valve. Now go back down and reconnect the hot supply using a coupler. I did not need to cut out the amount from the added fittings because there was plenty of room for the extra length of the fittings. I now have about a 1 second spot of cold before the preset temp comes back. WHAT A DIFFERENCE….. I found all of the fittings I needed at zoro.com that claims to have more than 300,000 fittings. Everything cost about $15 including shipping. The coupler, ½” CTS, PEX, White Product Number G4389287 Stock #16T737 PE10420. Along with the coupler be sure to get the Coupler ½” inserts Product Number G4388255 Stock # 16T768 (Two each). Check Valve, Polysulfone, ½ inch Product Number G2781064 Stock # 1DAT2 (No inserts needed with check valve) PLEASE CALL THEM TO CHECK THE NUMBERS These fittings are for PEX tubing. PLEASE check these numbers before ordering just incase I have made a typing mistake. This should work on any RV if you can locate the shower water lines going into the heater and there is room to cut/add coupling.