Fill loft cold tank with shower pump?

[foggys916]

OK

Had dormers fitted in my bungalow. The cold water tank in the loft is now smaller than the original one (space limited). Vented gas CH system with a tank. The cold gravity feed from the loft tank is 15mm the gravity feed to the hot water tank is 22mm.

Have a power shower in the upstairs bathroom and the pump for this is lower than the tank (2.5 meters).

After two showers the hot water stops coming through (stops completely, doesn’t just run cold). It’s a bit tricky to assesses whether the cold stops as the gravity cold is used just for the shower and the sinks are mains fed.

I suspect that the cold tank being emptied (head pressure loss) by the hot 22mm feed and 15mm cold feed, means an air pocket is created. As the tank is refilled by a cistern and is slow to refill, what are thoughts about having a shower pump, on the cold tank fill line (mains pressure), to boost the speed at which the tank is refilled? The pump would be triggered by the cistern flow and stopped by the ball lift as per normal.

Thoughts?

 

[Madrab]

Is it a shower fed by a pump or a shower that looks like an electric shower that has the pump inside the case? The former is just a pumped shower, the latter is a power shower, either or will will have gravity feeds as suggested for both hot and cold so yes, chances are the Cold Water Cistern (CWSC) is being run dry.

You can't use a shower pump on the mains, max pump on the mains is 12L/Min @ ~1.5bar that is if the shower pump would even work, which is debatable, it isn't designed to pump mains water and if it did it could create all sorts of problems.

What may be needed is the feed to the CWSC increased to 22mm and the ball valve enlarged and the mains flow assessed to confirm it can supply the CWSC properly. Alternatively a pump designed to pump the mains but that'll only work is the mains flow drops below 12L/Min.

 

[foggys916]

Actually I wondered if just replacing the inlet/cistern valve, which has been in place for a few years, might help and this is what I found. We’re in a very hard water area. Can hardly blow puff through the open valve.

Replaced and flow is much, much better.

Sometimes best to think of the simple things first!