I want to add a hot water recirc line to my trailer

[Bluebeard]

My wife runs the water in the sink until she gets hot water. When dry camping, that wastes a lot of water. I want to run a recirc line by cutting into my hot water line at the farthest point from the hot water heater, put a tee on it and have a switched valved that when turned on, opens and recircs the cold (but warming) water back into the fresh water tank. Does someone make a bulkhead fitting that you can use to insert from the outside and screw it tight from the outside to keep it from leaking? Since you cannot reach into those tanks, there is no way for you to hold a nut tight on the inside. I thought I searched on the net and found one, but I guess I didn't bookmark it. Any ideas?

[Bluebeard]

C Oneil- if you are hooked up to city water, chances are that using a bit extra water isn't a big deal, as you are also probably hooked up to a septic system. This valve idea (in my case) would be specifically used for boondocking. If you were hooked up to utiliites, I could see the other circ ideas of having extra circ pumps installed, so not waste water.

[c_oneil]

I installed a recirc line in my motor homne and am very happy with it. I put a 'T' in the hot water supply line to the kitchen faucet (this is the furthest faucet from my hot water tank). The water from the 'T' is plumbed through a plastic ball valve inside the door of the faucet cabinet and then routed through a hole in the floor to a 'T' at the outlet of my fresh water tank. When you open the ball valve the cool water in the hot water line is pumped by either city water pressure or by the fresh water electric pump back into the outlet line of the fresh water tank where there is no pressure. It only takes 10-15 seconds and then you turn off the ball valve. The water from the kitchen faucet is now immmediately hot and not a drop goes into the grey tank waiting for hot water. One small drawback is that when hooked up to city water and while the ball valve is open you are adding fresh water to you tank. If you were to turn on the valve and walk away you would over fill your fresh tank at some point. Never happened so far. It would just spill out the vent tube anyway.

[Specularius]

To answer the original question, the fittings for the fresh water tank are spin welded to the tank. Basically the fitting is spun and the friction melts the plastic to form a weld.

[RCMAN46]

brulaz wrote:

CJW8 wrote:
I have installed these in my home before with good results. Only $199 complete. Downside is 120 VAC. Since I'll be on a pedestal all winter I am considering one for freeze protection as others have said.

So how does that work?
The pump is mounted right on the hot water tank and some sort of non-electric cross-valve at the bath sink? Does it just continually leak water from the hot line to the cold or ... ?

Correct it leaks a small flow of water from the hot side to the cold until the hot side is above 95 degrees.

The disadvantage is the cold water line back to the hot water tank will always be warm until you use enough cold water to flush the warm water out.

I have this sytem in my home for the bathrooms. In my case it is not a problem as the kitchen where I would not want warm cold water is on the opposite side of my house from the hot water tank.

[Leaf-Peeper]

Here's some photos (with notes) of our hot water recirculation system.

https://www.flickr.com/photos/120944857@N06/13289564183/in/dateposted-public/

[CJW8]

brulaz wrote:

CJW8 wrote:
I have installed these in my home before with good results. Only $199 complete. Downside is 120 VAC. Since I'll be on a pedestal all winter I am considering one for freeze protection as others have said.

So how does that work?
The pump is mounted right on the hot water tank and some sort of non-electric cross-valve at the bath sink? Does it just continually leak water from the hot line to the cold or ... ?

brulaz,

Yes, I think the crossover has a setpoint of 95 degrees. The ones I installed, the pump was installed at the last fixture so no crossover valve was needed. It worked very well. On this system as you say the pump is at the WH so the crossover is needed at the last fixture. You can get extra crossovers if you have long branches off of the main run. Probably not necessary in an RV. I like the idea of the pump being at the WH because it will not take precious space in under the kitchen sink.

[Bobbo]

All you need to do is run a shunt from the hot water line under the sink to the cold water line. Put a backflow check valve to keep the water from flowing backward, and a small water pump. Turn on the pump and it pulls water from the hot water line, and recirculates it back into the cold water line. Brings hot water to the faucet without wasting any water at all.

[brulaz]

CJW8 wrote:
I have installed these in my home before with good results. Only $199 complete. Downside is 120 VAC. Since I'll be on a pedestal all winter I am considering one for freeze protection as others have said.

So how does that work?
The pump is mounted right on the hot water tank and some sort of non-electric cross-valve at the bath sink? Does it just continually leak water from the hot line to the cold or ... ?

[brulaz]

JaxDad wrote:

...
Your unit has one pump now, likely right next to your fresh water tank, it has a built in pressure switch that turns the pump on when the water pressure downstream drops below about 35 psi and shuts the pump back off again when pressure builds back up to around 50 psi.

This setup means every portion of the water system, be it hot or cold, downstream of the pump is under pressure, the SAME pressure created by one single pump.

What you are proposing is to merely add a few more feet of plumbing within that same, equalized pressure system. Without a difference in pressure between the two ends of a tube nothing will flow until you put a pump between those two ends.

12genusa tee'd in on the suction line of the pump, so there is a difference in pressure, and he says it works fine.

Personally I like myredracer's extra pump at the bath faucet idea because putting in an extra line would be a real pain in my trailer. That pump would have to be a special one though to handle the heat, and you wouldn't want it to passively allow water through when only one faucet is opened.

[JaxDad]

Bluebeard wrote:
JaxDad- I understand what he is saying, but he is suggesting I buy ANOTHER pump to put on my system. Why can't I use the pump I have? In other words, by teeing into the pressure line near the hot tap at my furthest point, the existing pump can do the circulation without adding another pump.

I think 12thgenusa is talking about what I was asking about. Either way, thanks for the input.

Your profile doesn't reveal what rig you have so I can't make specific comments, but rather just in general.

Your unit has one pump now, likely right next to your fresh water tank, it has a built in pressure switch that turns the pump on when the water pressure downstream drops below about 35 psi and shuts the pump back off again when pressure builds back up to around 50 psi.

This setup means every portion of the water system, be it hot or cold, downstream of the pump is under pressure, the SAME pressure created by one single pump.

What you are proposing is to merely add a few more feet of plumbing within that same, equalized pressure system. Without a difference in pressure between the two ends of a tube nothing will flow until you put a pump between those two ends.

[CJW8]

I have installed these in my home before with good results. Only $199 complete. Downside is 120 VAC. Since I'll be on a pedestal all winter I am considering one for freeze protection as others have said.

[Bluebeard]

JaxDad- I understand what he is saying, but he is suggesting I buy ANOTHER pump to put on my system. Why can't I use the pump I have? In other words, by teeing into the pressure line near the hot tap at my furthest point, the existing pump can do the circulation without adding another pump.

I think 12thgenusa is talking about what I was asking about. Either way, thanks for the input.

[12thgenusa]

Don't listen to the naysayers. I did the very mod you are suggesting and it works perfectly fine. Instead of cutting a new hole in the tank I cut the pump supply hose right close to the tank and installed a tee. link
It takes about 10 seconds of operation to get hot water up to the bathroom faucet. You won't get hot or even warm water into the fresh water tank unless you continue to let the bypass run.

[JaxDad]

Bluebeard wrote:
Smkettner- I guess that is another option, but I don't have $217 I want to spend on another pump. I think my idea is much easier and cheaper.

I think you're missing what they're trying to tell you.

The water pump comes on when the pressure drops DOWNSTREAM of the pump drops below the set point. Both the INPUT to the hot water heater and the OUTPUT of the water heater are downstream of the pump.

In other words, without a recirculating pump between your T fitting at the tap and the T fitting at the water heater, NOTHING will flow anywhere. They are both under the same pressure with nothing to cause a flow.