i have an indirect cylinder system, had a new cylinder und 3 way valve fitted in the summer, life was good.
last couple of days i have relented and put the heating on, then i find the water from the taps is getting to be just about warm, if i switch over to hot water only the tap water gets hot but goes down to tepid over about 2 days, when the switch is flicked to HW and CH the rads get really hot but not the tap water...any ideas chaps and chapesses ?

Sounds like when the three way valve is in the mid position most the water is going around the rads. Is there a slightly closed valve on the cylinder side?

thanks for the reply, rads stay cold when it,s in HW only, of the 2 outlets on the valve, 1 gets hot when on HW, both when on HW /CH
looking on tinterweb it seems that the water in the coil gets hot and that heats the water in the tank ?

Yes that's right, inside the cylinder is a spiral of copper that indirectly heats the water in the cylinder, so you don't end up with mucky chemical radiator water in your hot tap water. The three way valve has three pipes, in, HW (to the cylinder) and CH (to the rads).

So it sounds fine when on HW, as it should only heat the Cylinder.

When in the mid position only the central heating gets hot and the taps are just warm.

When on CH only, I assume just the heating gets hot (you'll get some heat creep along the pipe to the cylinder so best to feel the outlet from the cylinder)?

If yes to the last question it sounds like a balance issue, where the water is taking the path of least resistance (hence wondering about a partially closed valve on the cylinder circuit) OR the three way valve is biased to CH when it's supposed to be in the mid position and possibly faulty. Sometimes the rubber flap can swell so the valve needs to be right over to let water through.

Conrod, m8, i may of misread your prognoses, but if i say what my system was doing, there could be a similar problem

For years in my house, if we selected hot water HW it would do so, but also heat the radiators upstairs it was no big deal, but in hindsight wasteful
this honestly went on for years, but we dont need hot water that much, as washing machine dishwasher and shower do it all them selves

However, earlier this year, if we selected HW, it would do so, but also all of the houses heating as well, and being a large 4 bed place, again very wasteful

So a plumber was called in, and the three way valve (rubber ball valve) was knackered, it was a BITCH to replace, as it was in the most inaccesable place known, and i helped as well!

Now the HW and CH system works, just as it should, and already since March this year, ive used less that 1/3 the gas average, than i have done over the last 5 years, thats how wastful it was heating up water !!

steve

i think Joneh wins the prize, path of least resistance would make sense.
Steve, the valve was replaced in the summer after the tank sprung a leak, ill call the plumber and get him to have a look as it will be under waranty
cheers peeps