I have obtained a plate heat exchanger with four 3/4" parallel threads. What union connections do I use to connect to 22mm pipe? I believe I need to use rubber washers, similar to a tap connector. Can someone point to a BES or Plumb Centre part number? thanks
Assuming that your heat exchanger has male threads, you need 3/4 Female Iron* to 22mm (solder or compression) fittings - and seal the threads with PTFE tape.
[Have a look at BES 6656 for the compression version]
Is this 3/4'' BSP parallel thread male or female ? It's just so I can point you to the exact thing.
Something like this:
Plate heat exchangers are predominately 3/4" male parallel threads. Virtually "all" Female BSP fittings have "parallel" threads. The OPs wording of "parrallel" would have given the clue. So two parallel threads, male and female, requires a seal between (washer), or no seal despite packing with PTFE tape. You can pack it with hemp and it will work, but I would not do it as a slight movement anywhere will crack the joint. An appliance connector, like the tails of a system or combi boiler, complete with a bend, would do. A Vaillant 22mm copper connector would do but needs to be ordered from HRPC, complete with washer.
A tap connector is no good as it has a lip that the fibre washer fits in. An appliance connectors mating surfaces has to be "flat" on both surfaces to accommodate the rubber washer. You can buy a 22mm compression x 3/4" tap connector and grind down the lip so it is all flat. It has to be flat though, so a bit hit and miss.
It is a 3/4" male parallel thread. The walls of the stainless steel pipe, or thread, are thick and it is very flat at the end of the tread. The walls are far thicker than a normal 3/4" bath tap thread.
So the end of the thread looks something like this ?
You'll also need a washer inside to stop any leaking past the end of the union with male and female parts.
It will not. The plate heat exchanger has a 3/4" "parallel" male thread. That fitting has a 3/4" "parallel" female thread. No good. Parallel to parallel is no good. The thread could be packed with hemp and it will do it, but if it is moved it may crack the seal and a leak. One of the threads has to be tapered to use without a washer. What is needed as an appliance connector like what is on a system boiler or combi which has a washer. I have never seen these on open sale, only special order.
Do you know the difference between parallel and tapered thread ? That's why I posted a link to washers too. A male thread needs a female thread to connect on, or did you never learn basic sex education either ?
And why the hell does this OE keep putting spaces between the ends of the sentences and the bloody "?" ? See, it's done it again. :-)
You don't say....
What you propose is dangerous. You are hoping the washer has enough surface, and the surface is flat, at the end of the female 3/4 BSP brass fitting to form a seal. All rather hit and miss. A dedicated appliance connector is the way.
Thanks to all. I will search out a boiler connector. I notice these tend to be around 18mm and bulge out to 22mm to accept 22mm pipe. Looking at them I think the smaller 18mm is so a washer can be fitted.
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