Hot and Cold Hot Water

Here is a link to an earlier post concerning your problem.

boogie_4wheel wrote:
On mine, after I get the temperature set and shut off at the shower head, it gets wicked hot again for 1-2sec on restart. Gotta aim it at the wall.

Same here with an Atwood WH and standard shower head w/ shut-off button. I hold a washcloth over the shower head when I turn it back on. The problem isn't as bad after I installed a 2-gallon expansion tank in the bathroom sink cabinet. My theory is that it gives more cold water on the initial valve opening.
Side note - I used to have weeping at the WH pop-off valve but installing the expansion tank seems to have fixed that problem.

TakingThe5th wrote:

Dutch_12078 wrote:
Our current coach doesn't have the hot/cold shower problem to any significant degree, but our previous coach did. I solved it in that one by installing check valves in each line right at the faucet set. That eliminated any chance of one line over pressuring the other.

Interesting. When my shower head drips, it drips cold water which must be the higher pressure. Odd when you think that hot water expands, so it must have more pressure, but the hot water line may actually be cooling while at rest so that would equate to LESS pressure.

Yes, I've heard of various RV's that go either way. Some get a long cold shot when the shower head valve is turned back on, while others get a hot shot. The check valves should work for both situations. All we had after installing them was the slightly cooler effect for a few seconds from the water in the lines cooling.

Dutch_12078 wrote:
Our current coach doesn't have the hot/cold shower problem to any significant degree, but our previous coach did. I solved it in that one by installing check valves in each line right at the faucet set. That eliminated any chance of one line over pressuring the other.

Interesting. When my shower head drips, it drips cold water which must be the higher pressure. Odd when you think that hot water expands, so it must have more pressure, but the hot water line may actually be cooling while at rest so that would equate to LESS pressure.

Our current coach doesn't have the hot/cold shower problem to any significant degree, but our previous coach did. I solved it in that one by installing check valves in each line right at the faucet set. That eliminated any chance of one line over pressuring the other.

Thanks everyone for your ideas. I also have the Oxygenics but in my case it doesn't seem to play for or against the cold water shot. I've often wondered if there was a way to stop the dripping water during shutoff and thus stop the water movement to hot or cold.

OldBiscuit-I like your first suggestion on the mixing valve, might give it a try.

I also can put up with the oddities of the shower. My technique is to put the washcloth up to the shower head and rinse it while waiting for warmer water. But I do worry about the scalding water, especially when I recall the faucet breaking while I was taking a shower. But mainly I worry about guests and grandchildren and DW.

I guess I been lucky,....have NEVER had a probablem (4 different RVs) w/hot or cold water after idling for a minute or 2. And I don't know why.
I do not have any bypass valves or mixing valves, etc etc. in the system.

Probably due to pressure differential between hot and cold water sources at the shower valve. If the cold water pressure overcomes the hot water at the valve, the shower hose will eventually be filled with cold water. The reverse could also be true, hot water source higher pressure than cold so results will be very hot water in the hose.
It should be possible to change the original shower valve to one of the newer anti-scald fixtures and that may partially solve the scalding problem.

The cold water when you fist turn on the shutoff valve happens to most everyone, especially with those Oxygenic water saving shower heads. Nice warm water after adjusting but the cold water for a second when you turn the shutoff valve back on.

Suburban uses 2 sets of thermostats for electric (120V AC) and for propane (12V DC) that are preset for 130*F & 170*F

There is an optional 120*F/170*F set for electric only.

OR optional 140*F/170*F sets for electric and propane.

One of the pitfalls of RV water heaters.........how to get adequate gallon capacity and be small enough.
Higher temp set t-stats accomplish that..........but turn on just hot water handle and you get water hot enough to scald. Hot/Cold need to be used at faucet.

Water heaters with 'mixing valves' allow even higher temp t-stats and then mix hot/cold to deliver 130*F water on hot system....still hot enough to scald.
More usable hot water but user still has to mix hot/cold at faucet.

Also higher temps inside WH tank help prevent/control bacteria growth

Shower......
When you turn off using shutoff on handle the hot/cold mix in faucet.
When you turn it back on you either get blast of very hot or straight cold.
Turning it towards wall prior to turning back on is one solution.

Adjustable aftermarket mixing valves can be installed on any water heater.
Just a matter of some fittings, valves, piping.
They can be adjusted (OEM are 'locked preset'----can be 'unlocked' and made adjustable) so higher temps can be used for water in tank and then control output temp so it isn't dangerous.

Aftermarket mixing valves...

WATTS

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