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Post Info TOPIC: Hot water preheater


RV-Dreams Community Member

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Hot water preheater


was just curious if anyone has ever tried a 110 tankless water heater as a preheater to the gas/electric hot water heater in your rv.  Some in my family like to take a long hot shower and the current heater can't keep up.  I was wondering if putting in a 110 tankless electric that hooks to the 110 15amp on the electric pole would heat the water up enough to make a difference.  Was not looking to spend $1200 on a new tankless ho****er system.

 

thanks

Shannon



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Welcome to the board, Shannon.

Along similar lines I was thinking of adding a solar pool heater to pre-heat the water. However after further thought, realized that if I am boondocking I couldn't use it (as I wouldn't have a hose to hook it to) and if in a FHU CG or RV park I could just use the showers in the bath house for free, long showers if needed.

Incidentally it's funny that the center of the word hot-water is a bad word - only a machine would catch something like that.

Chip

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Shannon,

I'm pretty sure some of the RV'ers have installed the tankless hot water systems, but for some reason, I'm not sure an external system operating on 110V and 15 amps would be capable of really heating water that well in an "on demand" situation.  I would think it would take a lot of electricity to operate enough coils (or whatever) to heat the water fast enough.  I'd think that the water going from the external system would, at best, have a tepid temperature.  And, unless that external system could be plumbed directly to the hot water heater, you'd also have that same tepid water throughout the whole water system of the RV.

Terry



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A friend put an electric on demand hot water heater at the far end of his house and it needed 80 AMPs of electricity to supply hot water for a shower. 15 AMPs is not going to do much.

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Just come on down to Texas in the summertime. Near San Antonio we do not need to even turn on the hot water to take a shower . Sometimes the water in the hose needs to be run through the pipes before it cools down enough to shower with.

 



-- Edited by jjhoyle on Monday 10th of August 2015 08:55:59 AM

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J and J Hoyle


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Thanks for the comments. I was not thinking of trying to use a 15 amp tankless as the only source of hot water, rather as a preheater to the electric/LP heater that the camper has.  I was wondering if the tankless could heat the water up enough that then the 6/10 gallon heater in the camper could heat the rest of the way and with the two working together provide enough hot water for a long shower.  The comments are great but was not sure if they were being made with the preheating in mind.

 

thanks

shannon



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Yes, mine was made with preheating in mind.  Otherwise, unless extra modifications in the plumbing was done, your slightly preheated water would still be going to all the faucets in the coach, including the cold water taps.

Terry



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Your plan of 15 amps is not going to work. It is simply not enough power to preheat the water if it is flowing. Basically, it will have no noticeable effect on your water. 

Some people HAVE adapted portable propane water heaters like the Ecotemp L5 for RV use. I actually use one of these to supply an outdoor kitchen and it does work well. My issue with RV use would be how to safely mount it. The person I know that used it mounted it outside and fed the RV with it. Thus, it was "portable" in the sense he mounted it when in camp and took it down when travelling. You could not permanently mount this IN an RV. It would burn it down. 

I use the Truma AquaGo hot water heater (TEST REPORT). It works well, even in cold weather and at 8500'. But it cost in the $1200 range MSRP. Basically, "you get what you pay for".....



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If you want more hot water, judging from the voices of experience so far... it's going to cost you. Alternatively, remember you are not living in a house with a huge water heater and a seemingly endless supply of hot water.  I would encourage your family members that like long showers to learn the "Navy" way. Otherwise, the campgorund showers are ... over yonder.nobiggrinsmile

Brian



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I am also looking at doing this...would love to know if it has been done. My plan is to pre-heat the water entering the RV and hope for 85-90 degrees on the cold side. I can deal with Luke-warm faucet and toilet water. The 110v electric tankless heater I found is 3400w which is a little less than 30a. My plan would be to get a 50a adapter to a standard 3 prong to plug to power the tankless heater (and keep the trailer on its own 30a plug on the power pole). Then convert the fittings on the tankless heater from pipe thread to hose thread. With pre-heated water entering camper, I am using less hot water from the hot water heater to mix with the cold side so that would be a longer shower, and with relatively low flow of 1.5-2 gallons per minute for a shower the pre-heated water that is refilling the hot water tank could likely keep up with staying hot if I have both gas and electric turned on for the camper’s water heater during the shower. Seems like this would work...would love to know if anyone has tried. I can find tankless heater, 50amp plug adapter and plumbing fittings on Amazon all for under $150 -pretty reasonable price for a long shower...

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Heater: Zerodis Electric Water Heater 110V 3400W Mini Tankless Instant Hot Water System for Bathroom Kitchen Washing(Black) https://www.amazon.com/dp/B07M5D8K9M/ref=cm_sw_r_cp_api_i_r4nmCb8AJT7AG Plug adapter - there are some that cost less, but this one powers 2 outlets on each side of the plug from each hot side of the 50a service and night have use for other side (charging golf cart): AC WORKS S1450F520-018 1.5FT NEMA 14-50P RV/Range/Geneator Plug to (4) NEMA 5-15/20R 20Amp Household Female Connectors Adapter Cord https://www.amazon.com/dp/B079MCLL9X/ref=cm_sw_r_cp_api_i_e6nmCbASJBK2D Thread adapters: FASPARTS 1/2" Female NPT FPT FIP to 3/4" Male GHT Garden Hose Thread Adapter Brass Fitting Fuel / Air / Water / Boat / Gas / Oil WOG House / Boat / Lawn / Power Wash / Irrigation https://www.amazon.com/dp/B013XV9MGA/ref=cm_sw_r_cp_api_i_V6nmCbGZZM5MP The variables would be the temp of the supply water (would want for when it is cold) so I would guess supply water would be around 50 degrees, length of hose feeding RV -the shorter the better (or put the unit close to the city water inlet) and outside temp. If cold outside, could put foam pipe insulation around hose, or try with a heated hose designed to keep hose from freezing to prevent temp loss from heater to RV. I have a seasonal campsite and we use it about 90 days a year- March - May and October-November can result in some pretty quick showers. During summer when the supply water temp is likely around 75 degrees, I can take a very long shower as running the gas and electric on the hot water heater can somewhat keep up.

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jvcoach23 wrote:

Some in my family like to take a long hot shower and the current heater can't keep up.


 

I am not convinced your theory will work as long as it uses the 6/10 gal water heater for the final.  It takes time to heat water, even when you run the HWH on both electric and propane.  If the water is moving, ie. someone taking a shower and leaving the water running all the time, there is just not enough time to heat the water in the tank.  The only solution I can see is to install an on-demand HWH that is designed to do exactly what you need.



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Note to All.

This is a three year old thread, and the original poster hasn't logged into the forums in over 2 1/2 years.  Any information here needs to be verified as to whether it is still valid.

Also, keep in mind that Howard prefers that we NOT revive old threads, those that are over 1 year old.

Terry



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