Hot water in cold pipes

[cas]

Hi Everyone.

We have a problem with the water system on our Bavaria 40 Cruiser.
We are getting hot water flowing through the cold taps.
Has anyone had this problem or know where to start looking.

A new pressure valve was fitted but did not solve the problem.

Any help or ideas would be appreciated. Thanks

[TeddyDiver]

Check backflow preventer in the feed line to the warm water tank. Pressure valve is just to release excess pressure by warming water..

[cas]

Thanks, will have a look when i get out to the boat on Sunday.

[Kalinka1]

Any chance that the lines have been switched at the hot water tank or taps. Is it always hot or just when you open the tap? It could be the line is too close to the engine and when it is running heat is transferred to the water hose. have this problem on our boat. Not really a problem we don't have pressure water so warm water is kind of refreshing to wipe the salt off

[cas]

Thanks, have a few things to try, both heads and stern shower have the same problem, worse when on shore power ( as water hotter). A Faulty one way valve would seam to be the answer but Syndicate partner and engineer on board at the moment don't think there is one.

[bstruebing]

Some check valves fit tight in a .5" line, no hose clamps or splice required .

[FionaJC]

We had hot water out the cold tap and vice versa in the heads. Turned out the coloured rings were on the wrong way round. We don't have any valves just taps.

[Qayaq]

Think you will find the dump for the pressure relief is plumbed into the pick up line of the water pump, not to the bilge which is more usual. Is the 2nd relief Faulty?

[Kenomac]

You sure it's not the way it's hooked up to the taps? Everything is hooked up bassackwards in our boat that's from the UK. Hot and cold taps reversed, wall sockets upside down, even the brake levers on our Bromptons are bassackwards.

Now we're just used to it.

[Djarraluda]

This is a very common issue in plumbing, when apprentices are left to do the pressure test.
If you have a Mixer tap, with the outlet blocked-off, perhaps for a transom shower or similar. Check the tap itself is closed. If it is open, then the two circuits are open as one.
Roger

[Scott Berg]

As noted, it's almost always the check valve between the cold water line and the water heater.

[MoorOrLess]

I have had this same problem with warm water in the cold side of the system. The cause was as Djarraluda identified, both valves on the stern shower were open.

[Suijin]

Originally Posted by Scott Berg

As noted, it's almost always the check valve between the cold water line and the water heater.

^^^ This. And often there is no check valve at all

If you only get hot water in the cold water line at the beginning of a run of the fixture (or a few seconds later, if the fixture is further from the heater, like a forward head), and then it starts running cold then this is almost certainly the cause. If the water continues to be hot after running the fixture for a bit, then your problem is elsewhere.

[cas]

Thanks all,
Arrived at the boat and will start looking into the problem.
what I believe is the non return, but the flow is against the direction of the arrow. Is this right? I would have thought the arrow was indicating the direction of flow.

[GordMay]

Originally Posted by cas

... I would have thought the arrow was indicating the direction of flow.

Yes, the “flow arrow” points in the direction of the flow.
Make sure the valve type will work in the installed position. For example, not all check valves will work in a vertical line with flow down, nor will conventional or 90-degree piston check valves perform in a vertical line without a spring to push the disc back into the flow path. The disc in some check valves extends into the pipeline when the valves are fully open. This could interfere with the performance of another valve bolted directly to the check valve.
If possible, install the check valve a minimum of five pipe diameters downstream of any fitting that could cause turbulence.