Chris Carr FISPE urges swimming pool engineers to be single main drain alert…
Way before the 1990’s, swimming pools in the UK were fitted with a single main drain and we thought nothing of it. However, over time, it became apparent that there is a serious risk of entrapment on a single main drain. Just imagine the situation when the pool owner found that the pool water level had dropped below the skimmers and consequently was pulling in air into the system, so they decide to close the skimmer valve/s to overcome the problem.
Now all the powerful suction would come directly from the main drain!. Fortunately, in the early 1990’s, SPATA updated their standards stating that all new build domestic pools must have at least two main drains to be fitted to a single suction return line. Nevertheless, there remains a significant number of pools which were built before that standard was introduced and they continue to operate with a single main drain.
So yes, the danger still exists. As pool engineers whenever we visit a swimming pool, we should make the pool owner aware of any safety issues verbally and then in writing. Fortunately, a few years ago, a device called: ‘Vac Alert’ was designed as an ideal retrofit to overcome the problem with pools operating with single main drains. This device can be installed in the customer’s pool plant room and takes around three hours to fit.
Vac-Alert can be set to allow air into the suction line should the main drain become blocked or even partially blocked. The introduction of air into the system will overcome the ‘hold down force’ of anyone who might be covering the main drain, thus lessen, or stop the risk of entrapment. Because the Vac-Alert is a mechanical device, it will require annual inspection and cleaning which should be undertaken as part of an opening routine for the pool each season.
For me, ‘Vac-Alert’ appears to be the most practical and economic solution for all those existing pools with only one single main drain. A bit like wearing a seat belt when we get in our cars and vans, as swimming pool specialists, we have a duty of care to our customers to advise them of the risks and equally importantly advise them of any options to overcome those risks.
Chris Carr F.I.S.P.E.
01795 841 747