I (think I) blew up my HEP2O DHW flow !!

[Andy Y]

I hope I’m posting this in the correct forum, so here goes:

The attached photo speaks for itself: ‘exploded’ 17-year old 22mm Hep2O barrier! My question is how/ why?

Let me be the first to recognise this may well be a naïve self-inflicted wound but here is the full story in the hopes I can get some constructive feedback/advice:

The pipe in question was the first 150mm of my HW flow immediately after a Grundfos UP 20-45 N 150. The pump duty is set to ‘1’. This was a replacement for an older Grundfos pump which had seized (because it was only very briefly connected and thus hardly ever actually used). The pump was originally fitted to speed delivery of HW to our kitchen sink (and external doggy shower) which is some 25 metres horizontally from our cylinder, a BASI Hydras HY150LIND. The pipe runs consist of a 22mm loop (flow /return) to the BASI and is ‘Tee-d’ onto a 15mm leg that serves the kitchen /doggy shower.

I’m a controls/automation tech so needless to say it took me forever and a day to get around to actually hooking up my own pump! The ‘exploded’ pipe occurred about a month after the pump was connected to the controls and thus regularly run. The controls consist of a flow switch on the return pipe which triggers a timeout-relay such that the pump shuts off automatically after about 12 mins from the initial flow signal. I discussed this with my plumber buddy and we agreed that once hot water was available at the kitchen sink there was little point in wasting power by having the pump continue to run. Of course this also means a short-duration run of the hot tap may well have the pump running after the tap is closed but as the 22mm loop would/should not be restricted by closing the kitchen tap – WHY DID THE HEP SPLIT? J Maybe it’s nothing to do with my control setup and pressure but the pipe was quite happy until the pump was recently put into service.

The BASI cylinder stat is set to 55’. I have just ordered a hot water thermostat so as to verify the actual water temperature that is passing through the pipe. Probably not relevant, but the boiler is a Glowworm 30sxi.

Please let me have your thoughts? Thanks in advance.

 

[townfanjon]

If thats hep its in the wrong fitting , thats a speedfit tee.

 

[Best]

Too much heat will break down the barrier pipe. Just goes like in your photo. But I have no certainty in what has caused that

 

[Andy Y]

If thats hep its in the wrong fitting , thats a speedfit tee.

Thanks, yes it is HEP but the Speedfit 'T' is not really relevant to the question. It has since been changed and the damaged piece of pipe replaced with 22mm copper.

 

[Andy Y]

Too much heat will break down the barrier pipe. Just goes like in your photo. But I have no certainty in what has caused that

Actually, I'm wondering if a combination of 'too hot' water and the environment that the pipe is installed in are the clues. The closet through which the HW flow is routed also contains the UFH manifolds and is regularly around 35'C in winter. Any idea what the external environmental maximum is for HEP2O?

 

[Sharp Point]

Plastic pipe isn’t supposed to be used on a secondary hot water circuit. A secondary hot water circuit should be installed in copper.

 

[ShaunCorbs]

and this is why plastic pipe cant be used on a secondary water pump / circuit

 

[ShaunCorbs]

If thats hep its in the wrong fitting , thats a speedfit tee.

aslong as you use the hep inserts its fine / you can use anyfitting town

 

[Best]

This all then also points to the unvented cylinder install and operation requiring a G3 plumber to check everything.

 

[Andy Y]

and this is why plastic pipe cant be used on a secondary water pump / circuit

Wavin's advisory seems to suggest that Hep2O can be used for DHW but not for CONTINUOUSLY pumped circuits. In my case the pump was typically only running for a matter of minutes per hour - or am I just splitting hairs here? I fully appreciate that real-world experience speaks louder than a sales claim
Actually the difference in hot water delivery time was minimal with or without the pump operating so I'm inclined to just remove it at this point. Thanks for all the input.