Concept for cold weather use of rPod water systems

Originally posted by offgrid If you just use the solenoid and thermostat it you shouldn't need to do anything else. Add a shutoff valve so you can redirect water between the hot and cold lines at the far end of the water system from the pump.  This is just a connection of the hot and cold lines together with a valve to shutoff like at the water heater correct? probably located at the garage sink since i have a 182g  or low point drain? That valve will be open in winter and closed in summer. Add a second shutoff valve between the cold line and the water pump(solenoid or pressure pump in the trailer?) which will be open in summer and closed in winter to make sure the pump feeds only through the hot water line in winter.  a little fuzzy on the second cuttoff, a T valve ?if closed how does water from the fresh tank reach the pump? wouldn't i just add a T to the hot water line to feed the solenoid input? The solenoid can go between the cold line and the fresh tank overflow line so it runs hot water back into the fresh water tank. Or you can run it back into the fresh tank drain, that might use less heat because you won't be trying to heat the bottom of the fresh tank from the top.   I used one of the little Chinese thermostats in another project to provide a precise temp control for the water heater. There is a thread on it on the forum.  It runs on 12Vdc which is available at the water heater controls and should be able to run a 12V solenoid valve just fine. The temp probe for the thermostat can go on the lowest place in the system (bottom of the fresh water tank or on the bottom of the pump feed line at the tank).  You can get 2 thermostats for $8 on Amazon and have a second one to adjust the water heater temp.  https://www.amazon.com/HiLetgo-Temperature-Controller-Thermostat-One-channel/dp/B07CH7W3XP/ref=pd_sim_328_2/145-8709395-3663044?_encoding=UTF8&pd_rd_i=B07CH7W3XP&pd_rd_r=c892e5d4-1e83-11e9-8739-9941e184f583&pd_rd_w=85MgR&pd_rd_wg=JxkeJ&pf_rd_p=18bb0b78-4200-49b9-ac91-f141d61a1780&pf_rd_r=WXCJRBAXMZMVQD4HQMAY&psc=1&refRID=WXCJRBAXMZMVQD4HQMAY  do they come with a cover?  A solenoid valve like this should work OK. You'll need some plumbing parts to connect it up.  https://www.amazon.com/SNS-2W025-08-Electric-Solenoid-Normally/dp/B0794XJGBF/ref=sr_1_5?crid=1SJGTGMTXP1KO&keywords=12v+solenoid+valve&qid=1548188854&sprefix=12v+solen%2Cfashion%2C261&sr=8-5.  CharlieM did this mod on another brand of trailer and has a link to it on this thread. i have studied charlie's thread and i am trying to go by his schematic of the flow and pump location.

So the solenoid is triggered by thermostat A.  The opening of the solenoid relieves pressure which triggers the pump to come on and cause recirculating water to flow through system.  Thermostat B controls the water heater and triggers the water heater to come on as the recirculating water is cooled by running through the lines and fresh water tank. At this point the water heater is on, the pump is running and the solenoid is open. The water heater will reach the set point temp and turn itself off according to set point of thermostat B. Thermostat A will cause the solenoid to close at the set point.  Thermostat A should be a low temp like 60 deg, for instance. Thermostat B should be normal hot water temp of say 125 deg. The pump will continue to run until pressure is restored to system.  Correct?